Patent ID: 6538513
Filing Date: 2003-03-25
Classification: H03F

Abstract:
A differential transconductance amplifier with common mode output control, comprising:a reference circuit that provides a reference signal; a current mirror input circuit, coupled to the reference circuit, that develops a differential input current in response to a differential input voltage, wherein polarities of the differential input current have a constant sum; a differential current mirror, coupled to the current mirror input circuit, that mirrors the differential input current into first and second high impedance nodes; a summing junction coupled to a first source signal via at least one resistive device, the first source signal referenced to a common source signal; first and second feedback amplifiers, each coupled to the summing junction and to a respective one of the first and second high impedance nodes, that develops a differential feedback current through the summing junction, the differential feedback current having a common mode current based on the reference signal; first and second feedback current mirrors, each coupled to the reference circuit and to the summing junction and to a respective one of the first and second high impedance nodes, that generates feedback current into the high impedance nodes from the summing junction in response to variations of summing junction voltage; and a differential output circuit, coupled to the high impedance nodes, that develops a differential output current.