An integrated circuit gain block is obtained by cascading a common collector stage with a complementary common emitter stage. The current density of the common emitter transistor is made sufficiently greater than that of the common collector transistor so that the common emitter V.sub.BE lowest worst case value is higher than the common collector V.sub.BE highest worst case value. This makes the circuit manufacturable in integrated circuit form and permits the circuit to operate from a single power supply potential that can be as low as the series combination of one V.sub.BE added to one transistor collector to emitter saturation voltage. The circuit has a high current gain and is amenable to incorporation into current boosted class B amplifier output stages.
A low-noise wide-band bipolar transistor amplifier in which distortion caused by non-linear transistor operating characteristics is substantially eliminated. An input signal is coupled to the base of a first transistor connected in an emitter follower configuration with the signal formed at the emitter of the first transistor coupled to the base of a second transistor. Currents are supplied to the first and second transistors by a current mirror circuit in such a manner that a ratio of the current supplied to the first transistor to the current supplied to the second transistor is made constant. An output signal is produced in response to current variations in a transistor of the current mirror circuit which supplies current to the second transistor.
A current mirror circuit arrangement wherein an output current is provided by an output transistor and coupled between the base electrode of the output transistor and a reference potential is a series combination of a resistor and a diode. Signals are fed to the base electrode of the output transistor from a voltage supply via an emitter follower circuit and a resistor is connected across the diode so as to share current with the diode to increase its impedance at low current values and consequently to improve the overall linearity of the output current input voltage characteristic.
Compensation for the current flowing in the collector resistance of a transistor is achieved by generating a compensating current of appropriate magnitude and polarity sense, and applying that compensating current to the base of the transistor. To this end, a voltage equivalent to that across the transistor emitter-collector path is applied across a current conductive device representative of the collector resistance. The current therethrough is then proportioned by a current amplifier and applied to the base of the transistor to be compensated.
An adaptive transistor drive circuit including a multiple-emitter transistor, at least one emitter of which is connected to the drive circuit. When the drive current causes the transistor to saturate, the emitter connected to the drive circuit conducts a portion of the drive current to limit saturation of the transistor. A current source provides drive current which varies as a function of the current conducted by the collector of the transistor so as to maintain the transistor in saturation as the collector current and operating temperature vary.
A bipolar differential amplifying circuit contains a pair of input transistors (3 and 4) for receiving a differential input signal, a pair of differentially-configured first and second transistor circuits (5 and 6) coupled to the input transistors, and a subtracting circuit (11 and 12) for comparing the sum of the currents through first collectors (5C.sub.1 and 6C.sub.1) of the transistor circuits with the current through a second collector (6C.sub.2) of the second transistor circuit to generate an output signal representative of the input signal. A PN diode (13) is coupled to a second collector (5C.sub.2) of the first transistor circuit. The voltages at the collectors are very close, thereby yielding a high common-mode rejection ratio for the input signal.
