Gain control circuit and method capable of easing leakage current influence

A gain control method carried out by a gain control circuit and capable of easing leakage current influence, comprising the following steps:

• a signal receiving step operable to receive at least one input signal;
• a signal generating step operable to generate an output signal according to the at least one input signal and a gain;
• and
• a gain selecting step operable to choose one among a plurality of gain schemes to determine the gain while each of the gain schemes is set between the at least one input signal and the output signal and includes a signal path and a grounding path, including:
• choosing a target gain scheme among the plurality of gain schemes;
• having the signal path of the target gain scheme be conducting and the grounding path of the target gain scheme be non-conducting;
• and
• having the grounding paths of all the gain schemes except the target gain scheme be conducting and the signal paths of all the gain schemes except the target gain scheme be non-conducting.

A gain control circuit capable of easing leaking current influence, comprising:

• an amplifier comprising an amplifier input end and an amplifier output end;
• an input impedance circuit, coupled between a signal input end and the amplifier input end, operable to provide one of a plurality of input impedances which comprise a first input impedance and a second input impedance;
• and
• an output impedance circuit, coupled between the amplifier input end and the amplifier output end, operable to provide one of a plurality of output impedances or a constant output impedance,
• wherein when a signal is transmitted via the signal input end, the first input impedance and the output impedance circuit, a switch coupled between the second input impedance and the amplifier input end will be non-conducting but grounded through another switch.