Abstract: A biasing circuit adapted for operative coupling to the first input terminal so as to provide a relatively high biasing impedance to ground at the first input terminal, said biasing circuit being adapted to controllably vary the DC-voltage signal which biases the transistor amplifier, whilst at least one component of the biasing circuit is configured to simultaneously form a low-pass circuit for filtering a noise component of the DC-voltage signal before the DC-voltage signal is provided to the first input terminal.

Abstract: A device for use in biasing a transistor amplifier with a DC-voltage signal, the transistor amplifier including: a first input terminal; a second input terminal; and an output terminal coupled to the second input terminal; wherein said device includes: a biasing circuit adapted for operative coupling to the first input terminal so as to provide a relatively high biasing impedance to ground at the first input terminal, said biasing circuit being adapted to controllably vary the DC-voltage signal which biases the transistor amplifier, whilst at least one component of the biasing circuit is configured to simultaneously form a low-pass circuit for filtering a noise component of the DC-voltage signal before the DC-voltage signal is provided to the first input terminal.