Patent ID: 7915953
Filing Date: 2011-03-29
Classification: H03F

Abstract:
1. An amplifier circuit comprising: a first multi-stage amplifier having a first amplifier and a second amplifier, the first amplifier having a first input, a second input and an output, the second amplifier having a first input and having an output coupled to a first output of the amplifier circuit, wherein the second amplifier is configured to place the output of the second amplifier in a high impedance state responsively to a first control signal; a second multi-stage amplifier having a third amplifier and a fourth amplifier, the third amplifier having a first input, a second input and an output, the fourth amplifier having a first input and having an output coupled to a second output of the amplifier circuit, wherein the fourth amplifier is configured to place an output of the fourth amplifier in a high impedance state responsively to the first control signal; the first input of the first amplifier coupled to receive a first signal to be amplified and wherein the first multi-stage amplifier is configured to have a first resistor coupled from the output of the second amplifier to the first input of the first amplifier; a first switch coupled in parallel with the first resistor; a second resistor coupled from the output of the fourth amplifier to the first input of the third amplifier; a second switch coupled in parallel with the second resistor; and a third switch coupled between the second input of the first amplifier and the second input of the third amplifier.