Patent ID: 6781449
Filing Date: 2004-08-24
Classification: H03F

Abstract:
An electronic output stage for amplifying differential input signals with a small voltage swing, the output stage comprising:a first input terminal, a second input terminal, a first output terminal, and a second output terminal; a controlled current source; a first transistor having a first terminal connected to said controlled current source, a second terminal, and a control terminal connected to said first input terminal; a second transistor having a first terminal connected to said controlled current source, a second terminal, and a control terminal connected to said second input terminal; a third transistor having a first terminal connected to a first supply voltage potential, a second terminal connected to said second terminal of said first transistor and to said first output terminal; a fourth transistor having a first terminal connected to the first supply voltage potential, a second terminal connected to said second terminal of said second transistor and to said second output terminal; said control terminals of said third and fourth transistors receiving respective drive signals formed from the input signals by amplifying and providing the input signals with an adjustable offset voltage; a voltage change of the input signals and drive signals at said first and third transistors and at said second and fourth transistors, respectively, behaving in opposite ways; and a mirror circuit for setting a current through said first and second output terminals and a voltage between said first and second output terminals, said mirror circuit having two input terminals carrying respective reference voltages and said mirror circuit controlling said current source and the offset voltage to cause a low level at one of said output terminals and a high level at another of said output terminals to correspond to each of the respective reference voltages.