TRANSCONDUCTANCE AMPLIFIERS

摘要

The invention relates to transconductance amplifiers in which an output current depends upon the difference between two input voltages, and to the application of such transconductance amplifiers in analogue-to-digital converters. A difference amplifier (300) is configured for providing an output current dependent upon a difference between a first input voltage (302) and a second input voltage (304). The difference amplifier comprises an input sampling capacitor (318) coupled to a first conductor of said input sampling capacitor and a current output (314) for generating said output current; and an input switch (308, 310) for selectively coupling a second conductor of said input sampling capacitor to a first input of said difference amplifier for receiving said first input voltage and to a second input of said difference amplifier for receiving said second input voltage. The difference amplifier is configured to, in a first state, couple said second conductor to one of said first and second inputs and apply a voltage to said first conductor and to, in a second state, couple said second conductor to the other of said first and second inputs to provide a voltage change to said transconductance amplifier input dependent upon said difference between said first and second input voltages.