Accurate, wide-band, low-noise variable-gain amplifier structures and gain control methods

摘要

Variable-gain amplifiers (VGAs) are provided that realize gain accuracy (e.g., over variations in temperature and fabrication processes) while also providing this accuracy over a wide bandwidth and without the signal-to-noise degradation typically associated with signal attentuating elements. Differential signal and gain amplifiers of these VGAs include current sources which are controlled by a common error signal S_err. The gain amplifier is supplemented by feedback structure that generates the error signal S_err and controls the amplifier's transconductance to be the ratio of at least one of currents and resistors. Because such ratios can be well matched (especially in integrated circuit realizations of the variable-gain amplifiers) and because the current source of the signal amplifier is also controlled by the error signal S_err, this wide-band, low-noise open-loop amplifier's gain is accurately controlled.