Patent ID: 7592848
Filing Date: 2009-09-22
Classification: H03F

Abstract:
1. An offset adjusting apparatus for adjusting an offset of an output signal output from an amplifier including an operational amplifier and an amplification circuit, the operational amplifier having a first input terminal to which an input signal is to be input via a first resistor, a second input terminal to which a reference voltage is to be applied, and an output terminal, a second resistor being connected between the first input terminal and the output terminal, a resistance value of the second resistor being controllable, the amplification circuit connected to the output terminal of the operational amplifier to provide an amplified output signal, the offset adjusting apparatus comprising: an adjustment resistor having a controllable resistance value, the adjustment resistor having a first end to which an adjustment voltage for adjusting the offset is to be applied and a second end connected to the first input terminal of the operational amplifier; a controlling unit configured to control the adjustment voltage applied to the adjustment resistor, to remove the offset of the amplified output signal output from the amplification circuit; and a gain adjusting unit configured to control the resistance value of the second resistor to set an amplitude level of the output signal to a predetermined level, and to control the resistance value of the adjustment resistor to set a ratio of the resistance value of the second resistor to the resistance value of the adjustment resistor at a predetermined value, based on the amplitude level of the output signal.