Patent ID: 7167051

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 having a resistance R 1 ; 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 amplifier including a first transistor (MN 1 ) coupled between said first output node and a circuit common point and biased with a bias current I bias1 , and said second amplifier including a second transistor (MN 2 ) coupled between said second output node and said circuit common point and biased with a bias current I bias2 ; 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 , said first transistor conducts a current I a =I bias1 −I R1 when VINP>VINN and a current I a =I bias1 +I R1 when VINP<VINN, and said second transistor conducts a current I b =I bias2 −I R1 when VINN>VINP and a current I b =I bias2 +I R1 when VINN<VINP; a current mirror arranged to mirror a current applied at a current input terminal to a current output terminal, said current output terminal coupled to a current output node; circuitry arranged to couple current I a to the current input terminal of said current mirror; and circuitry arranged to couple current I b to said current output node.