Patent ID: 8026761
Filing Date: 2011-09-27
Classification: H03F

Abstract:
1. An instrumentation amplifier having gain and offset calibration using constant current sources and sinks, comprising: a first transconductance stage having positive and negative voltage inputs, and positive and negative current outputs; a second transconductance stage having positive and negative voltage inputs, and positive and negative current outputs; a trans-impedance amplifier having positive and negative current inputs and a voltage output; the positive current outputs of the first and second transconductance stages and the positive current input of the trans-impedance amplifier are coupled together; the negative current outputs of the first and second transconductance stages and the negative current input of the trans-impedance amplifier are coupled together; a first plurality of constant current sources; a first plurality of switches, wherein the first plurality of switches selectably couple certain ones of the first plurality of constant current sources to the first transconductance stage; a second plurality of constant current sources; a second plurality of switches, wherein the second plurality of switches selectably couple certain ones of the second plurality of constant current sources to the second transconductance stage; a third plurality of constant current sinks; a third plurality of switches, wherein the third plurality of switches selectably connect certain ones of the third plurality of constant current sinks to the positive current outputs of the first and second transconductance stages; a fourth plurality of constant current sinks; and a fourth plurality of switches, wherein the fourth plurality of switches selectably couple certain ones of the fourth plurality of constant current sinks to the negative current outputs of the first and second transconductance stages; whereby gain adjustment of the instrumentation amplifier is provided by selectably coupling the certain ones of the first and second plurality of constant current sources to the first and second transconductance stages, respectively; and whereby input offset adjustment of the instrumentation amplifier is provided by selectably coupling the certain ones of the third and fourth plurality of constant current sinks to the positive current outputs and the negative current outputs, respectively, of the first and second transconductance stages.