Amplifier and display apparatus employing the same

Claims

What is claimed is:

1. An amplifier including a push-pull circuit having two active elements and two points at which electrodes of said two active elements interconnect, wherein one of the two interconnection points is made an input end, the other interconnection point is connected to one terminal of a peaking capacitor for use in setting a gain, another terminal of said peaking capacitor being connected to an AC ground point and one of remaining non-interconnected electrodes of said two active elements is made an output end of the amplifier.

2. The amplifier according to claim 1, wherein said peaking capacitor is comprised of a through-hole capacitor having a capacitance between a pipe and a lead wire passing through the pipe, wherein both ends of the lead wire passing through the pipe are short-circuited there across outside the pipe to form a first end, and the pipe end is made a second end, thereby producing the capacitance between the two ends.

3. The amplifier according to claim 1, wherein said peaking capacitor is comprised of a through-hole capacitor having a capacitance between a pipe and a lead wire passing through the pipe, wherein any one of the ends of the lead wire passing through the pipe is made a first end, the other remaining end of the lead wire is connected with another capacitor, and the pipe end is made a second end, thereby producing the capacitance between the first end and the second end.

4. The amplifier according to claim 1, wherein said peaking capacitor is comprised of a three-electrode capacitor made so that one of two ends for producing a capacitance there between is branched into two leads, wherein the two leads are short-circuited with a lead wire to form a first end, and the other end of the two ends for producing the capacitance is made of a second end, thereby producing the capacitance between the first end and the second end.

5. An amplifier including a push-pull circuit comprising two transistors, wherein each of the first and second transistors forming said push-pull circuit has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected to an input end of the amplifier, the second electrode of said first transistor has a peaking capacitor connected therewith and also is connected with the second electrode of said second transistor, said second transistor of a polarity inverse to said first transistor, the first electrode of said second transistor is connected to the input end, and the third electrode of said first transistor is connected to an output end of the amplifier.

6. An amplifier including a push-pull circuit including two transistors wherein each of the first and second transistors forming said push-pull circuit has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, and a first current mirror circuit and a second current mirror circuit wherein:

the first electrode of said first transistor is connected to an input end and the second electrode of said first transistor has a peaking capacitor connected therewith and also is connected with the second electrode of said second transistor, said second transistor of a polarity inverse to said first transistor, the first electrode of said second transistor is connected to the input end, and the third electrode of said first transistor is connected to an output end; and

the third electrode of said second transistor is connected to an input end of said first current mirror circuit, an output end of said first current mirror circuit is connected with an input end of said second current mirror circuit, and an output end of said second current mirror circuit is connected with said output end of the amplifier.

7. An amplifier including a peaking capacitor and a push-pull circuit including two transistors, each of the two transistors having a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, characterized in that:

one end of a peaking capacitor is connected to an input end of the amplifier, the other end of the peaking capacitor is connected with the second electrode of a first one of the two transistors and also is connected with the second electrode of the second one of the two transistors, the second transistor of a polarity inverse to said first transistor, the first electrode of said first transistor is interconnected with the first electrode of said second transistor, and the third electrode of said first transistor is connected to an output end of the amplifier.

8. An amplifier including a first transistor and a push-pull circuit including two additional transistors referred to as second and third transistors, each of the three transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein the first electrode of the second transistor is connected to an input end and a second electrode of said second transistor has a peaking capacitor connected therewith and also is connected with the second electrode of said third transistor, said third transistor of a polarity inverse to said second transistor, the first electrode of said third transistor is connected to the input end of the amplifier, and the third electrode of said second transistor is connected to an output end of the amplifier; and

the third electrode of said third transistor is connected through a capacitor with the second electrode of said first transistor, and the third electrode of said first transistor is connected with the third electrode of said second transistor.

9. An amplifier including a first transistor and a push-pull circuit having two transistors, which are referred to as said second and third transistors, each of the transistors having a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein:

the first electrode of said second transistor is connected to an input end of the amplifier and a second electrode of said second transistor has a peaking capacitor connected therewith and also is connected with the second electrode of said third transistor, said third transistor of a polarity inverse to said second transistor, the first electrode of said third transistor is connected to the input end, and the third electrode of said second transistor is connected to an output end of the amplifier; and

the third electrode of said third transistor is connected through a constant-voltage circuit with the second electrode of said first transistor and the third electrode of said first transistor is connected with the third electrode of said first transistor.

10. An amplifier including a first transistor and a push-pull circuit having two transistors which are referenced to as second and third transistors, each transistor having a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said second transistor is connected to an input end of the amplifier and a second electrode of said second transistor has a peaking capacitor connected therewith and also is connected with the second electrode of said third transistor, said third transistor of a polarity inverse to said second transistor, the first electrode of said third transistor is connected to the input end of the amplifier and the third electrode of said second transistor is connected to an output end of the amplifier; and

the third electrode of said third transistor is connected through a capacitor with the second electrode of said first transistor, the third electrode of said first transistor is connected with the third electrode of said second transistor, and the third electrode of said third transistor is connected with an impeder of high impedance, such as a constant-current circuit, resistor or coil.

11. An amplifier wherein a feedback impeder is connected between an input end and output end of an inverted amplifier including a first transistor and a second transistor, said second transistor of a polarity inverse to said first transistor, said transistors having collectors thereof or drains thereof connected with each other and also connected with an output end of said inverted amplifier, bases thereof or gates thereof connected with each other and applied with a signal, and emitters thereof or sources thereof connected to an ac grounding point, the output end of said inverted amplifier is connected through an impedance conversion amplifier with an output end of the amplifier, and the input end of said inverted amplifier is connected to an input end of the amplifier.

12. The amplifier according to claim 11, said amplifier further including:

a third transistor inserted at a junction of one end of said feedback impeder, said input end of said inverted amplifier and said input end of said amplifier,

said third transistor having

a base thereof or a gate thereof connected with said input end of said amplifier,

an emitter thereof or a source thereof connected with one end not connected with said output end of said inverted amplifier of two ends of said feedback impeder, and

a collector thereof or a drain thereof connected with said input end of said inverted amplifier.

13. The amplifier according to claim 11, said amplifier further including

a third transistor inserted at a junction of one end of said feedback impeder, said input end of said inverted amplifier and said input end of said amplifier,

said third transistor having

an emitter thereof or a source thereof connected with one end not connected with said output end of said inverted amplifier of two ends of said feedback impeder and said input end of said amplifier,

a collector thereof or a drain thereof connected with said input end of said inverted amplifier, and

a base thereof or a gate thereof connected to an a/c ground point.

14. The amplifier according to claim 11, wherein said emitter or said source of said third transistor is connected to an a/c grounding point via a resistor.

15. An amplifier including a first transistor and a second transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected to an input end of the amplifier, and also is connected with the first electrode of said second transistor, said second transistor of a polarity inverse to said first transistor, and further is connected with one end of a feedback impeder, the third electrode of said first transistor is interconnected with the third electrode of said second transistor and also is connected with the other end of the feedback impeder, and the interconnection point of the third electrode of said first transistor, the third electrode of said second transistor, and the other end of the feedback impeder is connected to an output end of the amplifier.

16. The amplifier according to claim 15 wherein said wideband amplifier circuit is covered over with a conducting plate to suppress spurious radiation therefrom.

17. An amplifier including a first transistor and a second transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected through a first dc coupling circuit, which includes a resistor, to an input end of the amplifier, the first electrode of said second transistor that is of a polarity inverse to said first transistor is connected through a second dc coupling circuit, which includes a resistor, to the input end, one end of a feedback impeder is connected to the input end, the third electrode of said first transistor is interconnected with the third electrode of said second transistor and also is connected with the other end of the feedback impeder, and the interconnection point of the third electrode of said first transistor, the third electrode of said second transistor, and the other end of the feedback impeder is connected to an output end of the amplifier.

18. An amplifier including first transistor and a second transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected through a first dc coupling circuit, which includes a buffer amplifier and a resistor, to an input end of the amplifier, the first electrode of said second transistor that is of a polarity inverse to said first transistor, is connected through said buffer amplifier and a second dc coupling circuit including a resistor to the input end, one end of a feedback impeder is connected to the input end, the third electrode of said first transistor is interconnected with the third electrode of said second transistor and also is connected with the other end of the feedback impeder, and the interconnection point of the third electrode of said first transistor, the third electrode of said second transistor, and the other end of the feedback impeder is connected to an output end of the amplifier.

19. The amplifier according to claim 18 wherein a signal current source is connected to the input end of the amplifier.

20. The amplifier according to claim 19 wherein the signal current source is connected to the input end through a third transistor, the first electrode of which is grounded.

21. The amplifier according to claim 18 wherein said signal current source is formed of an integrated circuit.

22. An amplifier including first transistor, a second transistor, a third transistor, and a fourth transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected to an input end of the amplifier and also is connected with the first electrode of said second transistor that is of a polarity inverse to said first transistor, and the second electrode of said first transistor is connected with the first electrode of said third transistor that is of a polarity inverse to said first transistor;

the second electrode of said second transistor is connected with the first electrode of said fourth transistor that is of a polarity inverse to said second transistor, the third electrode of said first transistor is connected with the second electrode of said second transistor is connected with the second electrode of said third transistor; and

the second electrode of said third transistor is connected to an output end of the amplifier via a first resistor and the second electrode of said fourth transistor is connected to said output end via a second resistor.

23. An amplifier including first transistor, a second transistor, a third transistor, and a fourth transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said second transistor is connected to an input end of the amplifier, a bias voltage generator circuit is connected between the first electrode of said second transistor and the first electrode of said first transistor that is of a polarity inverse to said second transistor, and the second electrode of said first transistor is connected with the first electrode of said third transistor that is of a polarity inverse to said first transistor;

the second electrode of said second transistor is connected with the first electrode of said fourth transistor that is of a polarity inverse to said second transistor, the third electrode of said first transistor is connected with the second electrode of said fourth transistor, and the third electrode of said second transistor is connected with the second electrode of said third transistor; and

the second electrode of said third transistor and the second electrode of said fourth transistor are both connected to an output end of the amplifier through respective impedance elements.

24. An amplifier including a first transistor, a second transistor, a third transistor, and a fourth transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected to an input end of the amplifier and also connected with a first electrode of said second transistor that is of a polarity inverse to said first transistor, and the second electrode of said first transistor is connected with the first electrode of said third transistor that is of a polarity inverse to said first transistor;

the second electrode of said second transistor is connected with the first electrode of said fourth transistor that is of a polarity inverse to said second transistor, the third electrode of said first transistor in connected with the second electrode of said fourth transistor, and the third electrode, of said second, transistor is connected with the second electrode of said third transistor;

the second electrode of said first transistor is connected through a capacitor to the first electrode of said fourth transistor, the second electrode of said second transistor is connected though an electrolyte capacitor to the first electrode of said third transistor; and

the second electrode of said third transistor and the second electrode of said fourth transistor are both connected to an output end of the amplifier.

25. An amplifier including a first transistor, a second transistor, a third transistor, and a fourth transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain there of as a third electrode, wherein

the first electrode of said first transistor is connected to an input end of the amplifier and also connected with the first electrode of said second transistor that is of a polarity inverse to said first transistor, and the second electrode of said first transistor is connected through a resistor with the first electrode of said third transistor that is of a polarity inverse to said first transistor;

the second electrode of said second transistor is connected through a resistor with the first electrode of said fourth transistor that is of a polarity inverse to said second transistor, the third electrode of said first transistor is connected to a first ac guiding point, the third electrode of said second transistor is connected to a second ac grounding point;

the second electrode of said first transistor is connected through a capacitor to the first electrode of said fourth transistor, the second electrode of said second transistor is connected through an electrolyte capacitor to the first electrode of said third transistor; and

the second electrode of said third transistor and the second electrode of said fourth transistor are both connected to an output end of the amplifier.

26. An amplifier including a first transistor, a second transistor, a third transistor, and a fourth transistor wherein each of the transistors has a base thereof or a gate thereof referred to as a first electrode, an emitter thereof or a source thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the first electrode of said first transistor is connected to an input end and also connected with the first electrode of said second transistor that is of a polarity inverse to said first transistor first transistor is connected with the first electrode of said third transistor that is of a polarity inverse to said first transistor;

the second electrode of said second transistor is connected through with the first electrode of said fourth transistor that is of a polarity inverse to said second transistor, the third electrode of said first transistor is connected with the second electrode of said second transistor; and

the third electrode of said second transistor is connected with the second electrode of said first transistor, the second electrode of said first transistor, the second electrode of said third transistor and the second electrode of said fourth transistor are both connected to an output end of the amplifier.

27. An amplifier including a first transistor wherein said first transistor has a base thereof or a gate thereof referred to as a first electronic, an emitter thereof or a source thereof as a second electrode, and a collector thereof as a second electrode, and a collector thereof or a drain thereof as a third electrode, wherein

the third electrode of said first transistor having at least one of the first electrode and the second electrode connected with one end of a first coil and with one end of a capacitor, one end of a second coil and the other end of the first coil are connected to an output end of the amplifier, and the other end of the second coil is connected with the other end of the capacitor and a voltage source via a resistor.

28. An amplifier comprising an amplifying means having a first end connected to one end of a constant-resistance circuit including an inductance connected in parallel with a first resistance, said first end also connected with an output end of the amplifier, and the other end of said constant-resistance circuit being connected to an ac grounding point via an output resistance of the same resistance as that of said first resistance.

29. A display apparatus comprising an amplifier including an amplifying means having a first end connected to one end of a constant-resistance circuit, which includes an inductance connected in parallel with a first resistance said first end also connected with an output end of the amplifier, and the other end of said constant-resistance circuit being connected to an ac grounding point via an output resistance of the same resistance as that of said first resistance, wherein said output end of said amplifier is connected with a driving terminal of a display device in said display apparatus.

30. An amplifier comprising a variable gain amplifier for amplifying an input signal before feeding out, a control signal source for feeding a control signal to the variable gain amplifier to control a gain of the amplifier, and an adder-subtracter to which the control signal that is fed to the variable gain amplifier by the control signal source is also fed, referred to as the branched control signal, which adder-subtracter takes the branched control signal into one input end thereof, takes an output of the variable gain amplifier into the other input end thereof, and performs addition or subtraction of both signals before feeding a result out as an output signal, wherein:

a fixed operating point at which a relationship between the input signal and the output signal is kept constant can be set at a desired point on an input output characteristic curve showing the relationship between the input signal and the output signal even if the gain of the variable gain amplifier is varied by changing the control signal fed from the control signal source to the variable gain amplifier.

31. The amplifier according to claim 30 wherein when the control signal fed to the variable gain amplifier by the control signal source is branched, the branched control signal is voltage-divided through a voltage divider circuit of two resistors before the adder-subtractor takes the branched control signal into one input end thereof, thereby making it possible to set the fixed operating point at a desired point on the input-output characteristic curve.

32. An amplifier comprising a control signal source, an adder-subtracter for taking an input signal into one input end thereof, for taking a control signal from the control signal source into the other input end thereof, and for performing addition or subtraction of both signals before feeding a result out, and a variable gain amplifier receiving an output of the adder-subtractor input to amplify before feeding out as an output signal and has a branched signal of the control signal from the control signal source fed thereto to control the amplification gain, wherein:

a fixed operating point at which a relationship between the input signal and the output signal is kept constant can be set at a desired point on an input-output characteristic curve showing the relationship between the input signal and the output signal even if the gain of the variable gain amplifier is varied by changing the control signal fed from the control signal source to the variable gain amplifier.

BACKGROUND OF THE INVENTION

The present invention relates to an amplifier, and more particularly concerns a high output, low power consumption amplifier.

Also, the present invention relates to a wideband amplifier, and more particularly concerns a high-amplitude, wideband amplifier useful in a picture tube drive circuit which needs a high amplitude output.

The present invention relates to an amplifier applicable to a signal processor useful in controlling a video signal for driving a display apparatus, such as a CRT display.

As the display apparatus is made to have higher resolution in recent years, the picture tube drive circuit tends to have wider frequency band, particularly in a computer display for CAD and CAM which requires a bandwidth as wide as 50 to 300 MHz. The voltage amplitude of the drive signal needed is around 30 V for a monochrome picture tube or as high as around 50 V for a color picture tube. The voltage amplitude is being made higher with current demand for larger display size.

As a result, it is a problem that the power consumption of the drive circuit is increased, resulting in that the circuit components are large sized and heavy weight. In connection with that problem, FIG. 2 depicts a circuit diagram illustrating a capacitive load drive circuit for a prior picture tube or CRT which is described in the Japanese Patent Application Publication No. 57-20724.

The prior capacitive load drive circuit in FIG. 2 operates as follows. A wideband signal fed from a signal source 1 to an input pin 2 is divided into a low-frequency component and high frequency component before being amplified to drive a capacitive load 6. The low-frequency component is amplified by a parallel feedback amplifier circuit formed of a transistor 25 having a feedback path of an input resistor 27, a feedback resistor 7, and frequency response compensation capacitor 28, with a temperature drift and a distortion suppressed. A collector current of a transistor 4 forming a bias constant-current circuit can be suppressed to suppress the power consumption of the amplifier circuit. The high-frequency component is amplified by a series feedback amplifier circuit formed of a transistor 26 having a feedback resistor 31 and a peaking capacitor 32. Both frequency components are composed at an emitter of a grounded-base transistor 3 before being fed out to an output pin 5.

The prior technique described above involves a problem that the wideband signal cannot be amplified to a sufficiently high signal amplitude. That is, if the prior capacitive load drive circuit in FIG. 2 is used to amplify the high-frequency signal to a high amplitude, there is often a side effect wherein the peaking capacitor 32, with the circuit power consumption suppressed, cuts off the transistor 26, resulting in insufficient output amplitude. Further detailed description is given below.

If the input signal falls down, the peaking capacitor 32 has to be discharged to make the voltage waveform at the emitter of the transistor follow the input signal. A maximum discharge current of the peaking capacitor 32, however, is suppressed to a bias current of the transistor. Therefore, in the state that the bias current of the transistor 26 is suppressed to suppress the circuit power consumption if the input signal of high amplitude falls down in a very short transition time, the peaking capacitor 32 cannot be fully discharged, causing the transistor 26 to be cut off.

Also, it is another problem that the frequency response of the feedback system of the prior technique affects the characteristics of the amplifier circuit. For example, a phase delay caused in the feedback network sometimes affects stability of the amplifier circuit too much to fully secure the frequency band. Also, if the frequency band of the feedback network is not fully secured, a shoot caused in the transient response of the amplifier circuit is too much to fully secure the frequency band for the amplifier circuit as described above.

Further, it is still another problem that a load effect of the feedback network sometimes deteriorates the high-amplitude, wideband output capability of the amplifier circuit. In FIG. 2, also, parasitic capacitance and parasitic inductance of the feedback circuit elements, including the input resistor 27, the feedback resistor 7, the frequency response compensation capacitor 28, and the transistor 25 deteriorate the characteristics of the amplifier circuit. Moreover, it is still another problem that the frequency response compensation capacitor 28 makes narrower the frequency band at the time of high amplitude output as it is loaded on the amplifier circuit, although it is used to improve the transient response characteristic of the amplifier circuit.

As the display apparatus is made to have finer definition in recent years, the picture tube drive circuit tends to have higher amplitude and wider frequency band.

The following describes an example of the amplifier used as the picture tube drive circuit described in the Japanese Patent Application Laid-Open No. 60-5693.

FIG. 49 depicts a circuit diagram illustrating the prior amplifier used as the picture tube drive circuit. The amplifier used as the picture tube drive circuit, as shown in FIG. 49, has a cascade amplifier formed of a grounded-emitter transistor 310 and a grounded-base transistor 311. The transistor 310 has a video signal input thereto. The transistor 310 also has at an emitter thereof an emitter peaking circuit 312 for increasing a signal gain of the picture tube drive circuit at a high-frequency range of the video signal. The transistor 311 has at a collector thereof an output resistor 313. The output resistor 313 also is connected in series with a parallel peaking circuit coil 314 for increasing the signal gain of the picture tube drive circuit at the high-frequency range of the video signal. An output signal V.sub.OUT is fed out of a collector pin of the transistor 311 before being connected to the picture tube.

The amplifier constructed as described above can have a wide band because of the cascade construction and the parallel peaking. In fact, however, as shown in FIG. 50 which is a circuit equivalent to the one in FIG. 49, the transistor 311 has some parasitic capacitors amounting to a total parasitic capacitance C.sub.S added onto on the collector. The parasitic capacitors include a load capacitor 315 of capacitance C.sub.L, a parasitic capacitor 316 of capacitance C.sub.C at the collector pin of the transistor 311, a parasitic capacitor 317 of capacitance C.sub.R of the output resistor 313 of resistance R.sub.L, a wiring capacitor 318 of capacitance C.sub.P, and an output capacitor 319 of capacitance C.sub.Ob of the transistor 311.

Let f.sub.BH denote an basic frequency band of the amplifier with no peaking made. The basic frequency band f.sub.BH is given by ##EQU1## The total parasitic capacitance C.sub.S is given by

It can be seen from Eq. (1) that the basic frequency band f.sub.BH is in inverse proportion to C.sub.S and R.sub.L.

In the prior technique, C.sub.S is too high to make wider the frequency ban of the amplifier. If the frequency ban of the amplifier is forcibly made wider with C.sub.S being too high, the value of R.sub.L has to be reduced. As a result, it is a problem that the power consumption of the amplifier is increased.

FIG. 69 depicts a circuit diagram illustrating a prior video amplifier for use in a color CRT display. In the prior circuit shown in FIG. 69, three color video signals R(red), G(green), and B(blue) are fed from the respective signal sources 604R, 604G, and 604B through the respective video signal processor circuits 615R, 615G, and 615B to the respective cathodes 603R, 603G, and 603B of a CRT 604. The video signal processor circuits 615R, 615G, and 615B must have wide frequency band and large output power characteristics, respectively.

The following typically describes operation of the R color circuit 615R only since the other color circuits are identical. An input signal voltage Vir is applied to a base of a grounded emitter transistor amplifier 606R and is inverted and amplified at a collector thereof before being fed out as an output signal voltage Vor. The output signal is applied to the cathode 603B of the CRT 604.

An operating point of the output signal voltage Vor can be adjusted with a cut-off adjustment variable resistor 608R. A voltage gain can be adjusted with a drive adjustment variable resistor 609R. An adjustable range of the operating point of the output signal voltage Vor can be limited with a resistor 607R. A resistor 610R, like the resistor 607R, limits the voltage gain adjustable range.

A prior white balance adjustment can be made by repeating cut-off adjustments of the primary color circuits and drive adjustments of at least two primary color video amplifier circuits.

The prior white balance adjustment process is described below by reference to FIG. 70 which shows input-output characteristic curves of the video amplifier circuit. In the input-output characteristic graph in the figure, Vi denotes the input signal voltage on the axis of abscissas, and Voo denotes the output signal voltage on the axis of ordinates. A solid straight line 650 in the graph is an input-output characteristic with a target white balance secured.

In FIG. 70, assume the white balance to be in a state that the input signal voltage is at values Vic and Vid, which can be achieved with the cut-off adjustment and the drive adjustment, respectively. Also, assume an initial state of the video amplifier circuit is of a characteristic indicated by a broken line 651. With the first cut-off adjustment, the characteristic is moved, or chiefly level-shifted, to the output voltage Voo, or the one indicated by a broken line 653, as shown by an arrow 652.

With the next drive adjustment, a voltage gain adjustment indicated by an arrow 654 is made to change the characteristic to the one indicated by a broken line 655. This ends the first white balance adjustment. However, it is a problem that as can be seen by an arrow 656, the drive adjustment adversely deviates the preceding cut-off adjustment.

Therefore, the prior video amplifier circuit involves such a problem that the cut-off adjustment and the drive adjustment interfere with each other. The white balance adjustment cannot be completed unless the adjustments are repeated.

Also, in the above-described prior technique, any of the video signal processor circuits 615R, 615G, and 615B has to have a wide range of the signal voltage, including the dc component input thereto. This means that any of the video signal processor circuits 615R, 615G, and 615B has to have a wide input dynamic range. However, it is another problem that with the input dynamic range enlarged, the output dynamic range and the power supply voltage must be made high, so that the power consumption of the circuit is increased.

Further, in the above-described prior technique, if a white color temperature displayed on the picture tube (CRT) 604 is varied by a user, drive adjustment variable resistors for the primary color circuits are allowed for the user to adjust. However, when the user who has no measuring instruments is allowed to do the drive adjustment that is the same as the procedures as in factory, it may happen that the output amplitude of any of the primary color signal circuit becomes too high. This results in a deterioration of the linearity of the video circuit and the picture streaks. On the contrary, it may happen that the brightness is made too low. Therefore, it is still a further problem that the brightness is changed with the color temperature varied and further, the white balance is lost.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a first object of the present invention to provide an amplifier capable of feeding out a high-amplitude, wideband signal without increasing power consumption.

If the value C.sub.S is reduced, the bandwidth of the amplifier can be made wider or can increase the value R.sub.L so that the power consumption of the amplifier can be made lower.

Therefore, a second object of the present invention is to make an amplifier have a wider frequency band or operate at a low power consumption, thus providing a wideband amplifier capable of feeding out a high-amplitude, wideband signal.

A third object of the present invention is to provide an amplifier applicable to a signal processor having at least one operating point on an input-output characteristic curve at which an input-output relationship can be held even with a varied gain. If the signal processor of the present invention is used in a video amplifier circuit, an already set cut-off adjustment cannot be deviated even with a drive adjustment made.

A fourth object of the present invention is to provide an amplifier applicable to a signal processor capable of making effective use of a signal dynamic range without enlarging the signal dynamic range.

A fifth object of the present invention is to provide an amplifier applicable to a signal processor of which a brightness cannot be changed and a white balance cannot be lost with a white color temperature changed.

In order to accomplish the above-mentioned first object, the wideband amplifier of the present invention has a first means of a peaking capacitor connected to an ordinary output end of a push-pull circuit, although in the present invention, the output end is not for output, but for setting a gain.

Also, in order to accomplish the above-mentioned first object, the wideband amplifier of the present invention has a second means of feedback network formed by connecting a feedback impeder of an output signal with a low impedance pin of an active element. Further, in order to accomplish the above-mentioned first object, the wideband amplifier of the present invention has a third means of an output signal detector section of high impedance connected with a feedback impeder. Further, in order to accomplish the above-mentioned first object, the wideband amplifier of the present invention has a fourth means of drive elements forming the push-pull circuit connected with a current signal distributor circuit. Still further, in order to accomplish the above-mentioned first object, the wideband amplifier of the present invention has a fifth means of an active element having an ac-connecting pin connected in one signal path with a part of the other signal path. Finally, in order to accomplish the above-mentioned first object, the wideband amplifier of the present invention has a sixth means of connecting a peaking element with a output resistor through a capacitor.

In order to accomplish the above-mentioned second object, the wideband amplifier of the present invention has a first means of ac-connecting one end of the output resistor. Also, in order to accomplish the above-mentioned second object, the wideband amplifier of the present invention has a second means of connecting a constant-resistance circuit between the output resistor and a collector pin of an output transistor. Further, in order to accomplish the above-mentioned second object, the wideband amplifier of the present invention has a third means of a bear chip type of output transistor in a way that parts of or all of the wideband amplifier is made a hybrid IC. Still further, in order to accomplish the above-mentioned second object, the wideband amplifier of the present invention has a fourth means of eliminating parts of a ground pattern on a rear side of a circuit board of ceramics when the wideband amplifier is made a hybrid IC.

In order to accomplish the above-mentioned third object, the amplifier applicable to the signal processor of the present invention has one input pin of an adder-subtracter connected with an output of a variable gain amplifier to which an input signal to be processed is fed. Also, a control signal source for controlling a gain of the above-mentioned variable gain amplifier is connected with the other pin of the above-mentioned adder-subtracter and to a gain control pin of the above-mentioned variable gain amplifier. Further, an output pin of the above-mentioned adder-subtracter is connected to an output pin of the signal processor of the present invention. Alternatively, the positions of the variable gain amplifier and the adder-subtracter can be replaced by each other.

In order to accomplish the above-mentioned fourth object, the amplifier applicable to the signal processor of the present invention has the input signal to be processed fed to one input Pin of a switch which is switched over on the basis of a periodically generated signal, such as a blanking signal, and has a dc signal of controllable level, such as a dc level control signal during blanking, fed to the other input pin of the switch. Also, an input pin of a dc component controller is connected to an output pin of the switch. Further, an output pin of the dc component controller is connected to the output pin of the signal processor of the present invention.

In order to accomplish the above-mentioned fifth object, the amplifier applicable to the signal processor of the present invention uses three variable gain amplifiers having a R, G, and B primary color signals input thereto, respectively. Three output pins of a gain controller are connected to the respective control pins of the three variable gain amplifiers. Output pins of the three variable gain amplifiers are connected to the respective output pins of the signal processor of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a circuit diagram illustrating a basic embodiment of the present invention for a wideband amplifier;

FIG. 2 is a circuit diagram illustrating a prior capacitive load drive circuit;

FIG. 3 is a circuit diagram illustrating an embodiment of the present invention;

FIG. 4 is a circuit diagram illustrating still another embodiment of the present invention;

FIG. 5 is a circuit diagrams illustrating another basic embodiment of the present invention;

FIG. 6 is a circuit diagrams illustrating still another basic embodiment of the present invention;

FIG. 7 is a circuit diagrams illustrating still another basic embodiment of the present invention;

FIG. 8 is a circuit diagram illustrating a practical embodiment of the pr