Patent ID: 6316970
Filing Date: 2001-11-13
Classification: H03F

Abstract:
A floating, balanced output circuit for providing a differential output voltage in response to an input voltage, with a relatively low differential output impedance and a relatively high common-mode output impedance, comprising:a first transconductance amplifier section for providing a differential pair of output currents in response to the input voltage, the currents being substantially equal in magnitude and opposite in polarity;an intermediate section connected so as to generate an intermediate differential voltage in response to the pair of output currents of the first transconductance amplifier;an output section for generating the differential output voltage in response to the intermediate differential voltage;a differential feedback loop configuration connected around the first transconductance amplifier section and the intermediate section so as to provide differential negative feedback; andcommon-mode feedback loop configuration comprising a second transconductance amplifier section connected around the intermediate section so as to respectively add a pair of substantially matched output currents to the output currents of the first transconductance amplifier stage in response to the common mode current;wherein the first and second transconductance amplifiers are designed so that the common mode feedback loop configuration remains active when the differential loop configuration has been disabled due to clipping when the input voltage exceeds a predefined level.