Patent ID: 6346854
Filing Date: 2002-02-12
Classification: H03F

Abstract:
An amplifier circuit for operating with a single power supply, comprising:a first amplifier having a controllable gain and being configured to be biased between a power supply voltage and a circuit ground, to receive a first reference voltage having a value between the power supply voltage and the circuit ground, to receive a first input signal, and to selectively operate in either a first mode in which an output signal of the first amplifier is substantially equal to the first reference voltage or in a second mode in which the output signal is substantially equal to a sum of the first reference voltage and a multiple of the first input signal; a controller configured to receive the first reference voltage and a second reference voltage, the controller being further configured to generate a control signal based on a comparison of the first reference voltage with the second reference voltage; and a delay mechanism, coupled to the controller and the first amplifier, configured to receive the control signal from the controller and to provide to the first amplifier a delayed control signal that is substantially equal but delayed in time to the control signal, the delayed control signal being operative to select between the first mode of the first amplifier and the second mode of the first amplifier, wherein, a turn-on event causes the controller to detect a change in the comparison of the first reference voltage and the second reference voltage, and in response to that change to generate the control signal, and further wherein the delay mechanism receives the control signal generated by the controller, delays the control signal by a predetermined delay, and, at the expiration of the predetermined delay, provides the delayed control signal to the first amplifier which switches between the first mode of operation and the second mode of operation based on the state of the delayed control signal.