Controllable amplifier circuit with a variable discrete-value gain, use of the amplifier circuit and method for operation of an amplifier whose gain can be adjusted in discrete values

A controllable amplifier circuit, comprising:

• a signal input, a signal output, and a control input;
• a control circuit configured to selectively vary a gain of the amplifier circuit based on a state of the control input;
• and
• at least two first amplifier stages arranged in parallel and connected in the signal path between the signal input and the signal output, and at least one second amplifier stage connected in the signal path between the signal input and the signal output, and
• wherein the first and second amplifier stages are coupled to the control circuit, wherein the control circuit is configured to produce a push-pull control signal for switching the at least one second amplifier stage for a switching process thereof, and configured to produce a single-ended control signal, after the switching process, for driving the at least two first and the at least one second amplifier stages thereafter.

A method for operation of an amplifier having a gain adjustable in discrete values, comprising:

• providing an amplifier circuit comprising first and second amplifier stages with a first gain and at least one third amplifier stage with a second gain different that the first gain;
• applying a signal to be amplified to the amplifier circuit;
• producing push-pull signals for selective adjustment of the amplifier stages to alter a gain of the amplifier circuit;
• adjusting an operation of the amplifier stages by means of switching and control signals derived from the push-pull signals;
• producing single-ended signals for the changed gain;
• supplying to the amplifier stages switching and control signals derived from the single-ended signals;
• and
• amplifying an applied signal with the changed gain.