Patent ID: 7884671
Filing Date: 2011-02-08
Classification: H03F

Abstract:
1. A folded cascode amplifier including a class-AB input terminal, the amplifier comprising: a first input unit to receive a first an A bias current, to transform a difference between an input voltage and an output voltage of the amplifier into a corresponding intermediate current, and comprising a plurality of input transistors; a second input unit to receive the intermediate current and a B bias current and to control a voltage output from the second input unit in response to a change in the intermediate current from the first input unit; and an output unit to output an output voltage to an output node controlled by an output control unit which receives the output voltage of the second input unit, and to generate a quiescent current to flow from the output control unit to a ground voltage source, wherein the first input unit comprises a first control circuit and a second control circuit each comprising one terminal connected to the output node and another terminal connected to a respective input transistor from among the plurality of input transistors, and wherein each of the first and second control circuits controls a current flowing into the plurality of input transistors and out of the plurality of input transistors, according to respective operating modes of the amplifier, whereby the B bias current and the quiescent current do not increase even when the A bias current is increased to increase a slew rate of the amplifier.