Patent ID: 7126412

Claim:
A pre-amplification circuit including: a current to voltage conversion and amplification first circuit; a second circuit receiving an output signal transmitted from said first circuit, as an input signal; a voltage dependent variable capacitance third circuit which is electrically connected to an input of said first circuit, and which a part of a current running into said input of said first circuit enters, said third circuit including a circuit electrically connected between said input of said first circuit and a grounded voltage, and comprised of a diode and a power source electrically in series to each other, wherein, the first circuit comprises a first transistor ( 5 ) and a first resistor ( 6 ), the first resistor electrically connected at one end to a second power source ( 17 ) and at another end to both a collector of the first transistor and a base of a second transistor ( 8 ), and the second circuit is an emitter follower buffer stage, having a first emitter follower buffer circuit.