Patent ID: 7119622

Claim:
An amplifier comprising: a substrate; a high side power supply terminal connected to an external constant-voltage source and maintained at a fixed high potential; a low side power supply terminal connected to one of an external constant-voltage source and a ground conductor, and maintained at a fixed low potential; an amplifier circuit with a MOSFET input stage that includes an input terminal connected to an external signal source, is embedded on said substrate, receives a signal of said signal source through said input terminal, and amplifies the signal at a predetermined rate; and a bias circuit embedded on said substrate and comprising: a bias voltage generating section that generates a predetermined bias voltage; and a MOSFET acting as an impedance device including a drain and a source, the one of which is connected to one of said high and low side power supply terminals, and the other is connected to the input terminal of said amplifier circuit, a gate maintained at the potential to prohibit the channel generation between said drain and said source, and a backgate electrically separated from said substrate and maintained at the potential equal to said bias voltage.