Abstract: The present invention is a high speed, low gain stable amplifier. The amplifier is for amplifying an input signal and providing an output signal to a known, fixed load. The amplifier has a first stage that is a differential amplifier that amplifies the input signal. The amplifier then has a second stage which is a push pull transconductance stage which operates at a low gain (approximately unity gain), and the transconductance of the push pull transconductance stage is approximately equal to the reciprocal of the impedance of the predetermined load. The push pull transconductance stage includes first and second driver transistors. These driver transistors control the output signal. The amplifier of the invention provides amplification of a wide bandwidth with minimal phase shift.

Abstract: The precision operational amplifier of the invention has at least two stages, a first input differential stage and a second high gain stage having its input coupled to the output of the first stage. A digital control circuit coupled to the output of the second stage is used to supply a correction signal to the first stage, the correction signal being calculated to compensate for the offset voltage of the first stage. A digital representation of the correction signal is stored so that it may continuously be applied to the first stage, whereby the offset voltage of the first stage is substantially reduced and such reduction can be maintained for long periods of times. In a preferred embodiment, the digital circuit supplies a second independent correction signal to the second stage. That signal is also stored so that it may continuously be applied to the second stage, whereby the offset voltage of the second stage is substantially reduced and that reduction too can be maintained for long periods of time.

Abstract: A low-level dc amplifier includes a first amplification stage having a pair of direct coupled inputs and a pair of outputs direct coupled to the input side of a second amplifier. A first double-pole, double-throw electronic switch interchanges the two first stage inputs synchronously with a second such switch which interchanges the two first stage outputs. The switches produce at the input of the second amplifier a signal which averages out the first stage's equivalent offset signal. A clock drives the two switches at a preselected clocking frequency. The two clock-driven switches effectively cancel out low frequency (1/f) noise. A filter at the output side of the second amplification stage removes higher frequency noise including clock frequency noise.