There is a need for providing a variable amplifier circuit suited for a semiconductor integrated circuit and a high-performance camera preprocessing LSI using the variable amplifier circuit. At first timing, a first input capacitor acquires a first signal. An amplifier circuit amplifies a second signal acquired to the second input capacitor according to a gain corresponding to a capacity ratio between the second input capacitor and a feedback capacitor composed of a variable capacitor device. At second timing, the second input capacitor acquires a second signal. The amplifier circuit amplifies the first signal according to a gain corresponding to a capacity ratio between the first input capacitor and the feedback capacitor. A variable gain amplifier circuit interleavingly amplifies the first signal and the second signal in synchronization with the first timing and the second timing.
Provided are a switched capacitor amplifier capable of removing an influence of an offset voltage and a 1/f noise using a simple circuit, and a method of operating the same.According to the present invention, a switched capacitor amplifier having an operational amplifier and switched capacitors includes: a first switched capacitor one terminal of which is connected with a plus (+) input terminal of the operational amplifier and another terminal of which is applied with an input voltage; a second switched capacitor one terminal of which is connected with a minus (-) input terminal of the operational amplifier and another terminal of which is applied with an input voltage; a third switched capacitor which is inserted between the plus (+) input terminal and a plus (+) output terminal and provided to set an amplification factor in cooperation with the first switched capacitor and store a plus (+) compensation voltage for compensating for an offset, which is applied to the plus (+) input terminal; and a fourth switched capacitor which is inserted between the minus (-) input terminal and a minus (-) output terminal and provided to set an amplification factor in cooperation with the second switched capacitor and store a minus (-) compensation voltage for compensating for an offset, which is applied to the minus (-) input terminal.
