Variable gain amplifier

摘要

A method may include applying an input differential voltage to input terminals of an amplifier, a first input terminal coupled to a gate of a first transistor and a second input terminal coupled to a gate of a second transistor. The method may also include varying a gain of the amplifier by varying at least one of: a resistance of a first resistor, the first resistor coupled between a source of the first transistor and a source of the second transistor; and a resistance of a second resistor, the second resistor coupled between a source of a third transistor and a source of a fourth transistor; wherein: the third transistor is coupled at its drain to the drain of the first transistor; and the fourth transistor is coupled at its drain to the drain of the second transistor and a gate of the third transistor and coupled at its gate to the drain of the third transistor.

主权项

1. A method, comprising:
applying an input differential voltage to input terminals of a variable gain amplifier, the variable gain amplifier comprising a gain stage and an active load stage; and varying a gain of the variable gain amplifier without altering a common mode output voltage of the variable gain amplifier by varying an effective impedance provided by the active load stage to the gain stage, wherein varying the effective impedance includes source degeneration of the active load stage.