Single ended instrumentation folded cascode amplifier

A method for obtaining high common mode rejection in an instrumentation amplifier, said method comprising the steps of:

• receiving a differential input signal in a differential input pair of the instrumentation amplifier;
• splitting output current mode signals provided from said differential input pair by a pair of folded cascode transistors and additional pair of transistors, configured as current buffers;
• summing a portion of output current mode signals provided from said additional pair of transistors;
• receiving the sum of the portion of the output current mode signals provided from said additional pair of transistors at an input of a current controlled current source;
• and
• providing an output current of the current controlled current source to a feedback network and to feedback inputs of the differential input stage.

An instrumentation amplifier configured for providing high common mode rejection and low distortion, said instrumentation amplifier comprising:

• an input differential stage configured to receive a differential input voltage and differential feedback voltage;
• a folded cascode amplifying stage configured to receive output current mode signals provided from said input differential stage;
• a current mirror configured to mirror output current mode signals provided from said folded cascode amplifying stage;
• an external gain setting stage including a first resistor feedback network, which includes a first resistor being connected between feedback inputs of said input differential stage, a second resistor between an output terminal of an output stage and a first feedback input of said input differential stage, and a third resistor between a common terminal and a second feedback input of said input differential stage;
• an output buffer and an output resistor, said output buffer configured to receive a differential current mode signal from the current mirror, said output buffer includes an output terminal to provide an output voltage to the first resistor feedback network, said output resistor being coupled to an input terminal of said output buffer;
• and
• wherein the external gain setting stage includes a second resistor feedback network connected between the input terminal of the output buffer and the first resistor feedback network.