Patent ID: 7170349

Claim:
A differential amplifier comprising: (a) first and second matched transistor means having respective first and second drains through which respective first and second drain currents flow, where the first and second drains coupling to respective first and second voltage output nodes of the differential amplifier, and where magnitudes of the first and second drain currents define a constant sum; (b) first and second, variable and matched drain impedances respectively coupled to the first and second drains, each of the variable drain impedances having at least two inductors (L 1 , L 2 ), an output shunt capacitance and a resistance, wherein at least said resistance is adjustable so that an output voltage versus input voltage transfer function of the differential amplifier can be tuned at least at 0 Hz (base frequency) by adjusting the resistance; and (c) first and second, variable current injectors respectively coupled to inject additional bias current into respective injection nodes interposed between the at least two inductors (L 1 , L 2 ) of each of the first and second variable drain impedances so that the injected additional bias currents increase drain currents of the respective first and second transistor means to magnitudes greater than magnitudes of voltage-dropping currents passing through the respective resistances of the first and second variable drain impedances, where at least one of the first and second inductors in each drain impedance separates the respective bias current injector from the corresponding voltage output node of the drain impedance.