Patent ID: 7567121

Claim:
A current-mode instrumentation amplifier (IA), comprising: first and second input terminals connected to receive a differential voltage (VINP−VINN); a first resistance element; first and second buffer amplifiers having respective input nodes coupled to respective ones of said input terminals and respective output nodes providing first and second output voltages V 1 and V 2 which vary with VINP and VINN, respectively, said first resistance element connected at a first terminal to said first output node and at a second terminal to said second output node such that said first resistance element conducts a current I R1 which varies with V 1 -V 2 ; a first circuit which produces a DC output current I DC1 which varies with V 1 and I R1 ; a second circuit which produces a DC output current I DC2 which varies with V 2 and I R1 ; said IA arranged such that when VINP=VINN, I DC1 =I DC2 ±I error , where I error arises due to mismatches between said first and second buffer amplifiers and/or said first and second circuits; and an auto-zero network arranged to reduce I error such that the magnitude of I error is less than it would be without said auto-zero network.