A method of adjusting the gain of an operational amplifier using a digital-to-analog converter (DAC) based upon R-2R resistive ladder technology inserts the DAC between the output of the operational amplifier and the non-inverting input to form a positive feedback loop. Variations of a digital control code applied to the DAC to control the gain are not affected by corresponding variations in the output resistance of the DAC so that undesirable changes in the magnitude of output noise, drift, ban...

An operational amplifier circuit having a first amplification stage that includes a differential pair of matches, low-noise transistors coupled in a common-emitter configuration, with a special reactive network in the emitter circuit of each transistor. Each reactive network comprises an inductor and a resistor, arranged in a shunt configuration, whereby at low frequencies the first stage has a relatively high gain and generates relatively low noise, and whereby at high frequencies the first sta...

Offset voltage compensation is provided by a feedback capacitor (24) in a feedback loop (20). For periodically resetting the compensation, the signal input terminal (14) is grounded by an electronic MOSFET switch (34). Other such switches (22, 26) close the feedback loop (20) in front of the capacitor (24) and connect the output side of the capacitor (24) to ground for recharging. An input capacitor (30) for compensating the switching feed-through charge of the feedback loop switch (22) is conne...

A camera having an automatic exposure control mechanism wherein aperture priority, shutter speed priority and manual modes of operation can be set without the possibility of the switching mechanism being set to inoperable positions. The aperture ring of the camera lens is provided with a protrusion which interlocks with a corresponding protrusion on a ring of the camera body through which aperture information is transmitted. The shutter dial of the camera is provided on its reverse side with plu...

An FM muting circuit has a common input terminal and uses an operational amplifier which has a pair of input terminals. The two amplifier input terminals are coupled to the common muting circuit input terminal. An electronic switch is connected between ground and one of the operational amplifier input terminals. When the muting circuit receives an input signal which is free of noise, a "high-level" control signal is developed to switch the electronic switch into a saturated condition, thereby gr...

A circuit which includes an operational amplifier (101) and includes switches (104, 106) for cancelling offset buildup in the amplifier in response to a circuit (110) which detects zero crossings of the input signal. Where the frequency of the input is higher than the frequency at which cancellation is necessary, circuit (110) may respond only to the zero crossing next following each of a regularly occurring series of timing pulses.

An operational amplifier having an extremely high gain-bandwidth product. The amplifier includes a gain cell with an active negative resistance circuit made up of two matched NPN transistors (18 and 20) with their bases cross-connected to their collectors, and with a differential pair of NPN transistors (14 and 16) having their emitters degenerated through the active negative resistance circuit. The value of the negative resistance is chosen to negate other resistance values in the denominator o...

An operational amplifier includes an input stage, an output stage including first, second and third NPN output transistors, and an intermediate stage. The first NPN output transistor sources load current to an output terminal while the second and third output transistors sink load current therefrom. A first Miller capacitor is coupled between the input of the intermediate stage and the amplifier's output terminal. A second Miller capacitor is coupled between the base and collector terminals of t...

A single stage high performance operational transconductance amplifier consists of a pair of p-channel load field effect transistors, a pair of n-channel type cascode field effect transistors, a pair of n-channel differential field effect transistors and an n-channel current source field effect transistor. This amplifier has improved performance in terms of noise and power supply rejection as compared to conventional CMOS amplifiers.

An operational amplifier is disclosed which is capable of handling input voltages in excess of 200 volts, comprising at least in the input stage thereof a plurality of low voltage transistors including at least a pair of low voltage lateral PNP transistors each having two collectors. These lateral PNP transistors act as level shifters for the amplifier and also a bias arrangement for the input stage. A single high voltage lateral PNP is in the signal path providing the lowest pole in the transfe...