A Feed-Forward Automatic-Gain Control Amlifier for Biomeducal Appications

A novel CMOS feed-forward automatic-gain control (FFAGC) amplifier is presented. The proposed amplifier is intended to amplify various kinds of biomedical signals with a wide dynamic range characteristic. The feed-forward automatic-gain control (FFAGC) technique is adopted to provide appropriate gain settings. Furthermore, a class-AB output stage realizes large driving ability for an external ADC. The experimental results showed that variable gains of 0 dB, 6 dB, 14 dB, and 20 dB with a bandwidth of 55 kHz, input referred noise of 200nV/root HZ at 500 Hz, rail-to-rail input common-mode range, and rail-to-rail output dynamic range can be achieved while the output loading capacitor is 330 nF. The power consumption is 819 mu W with 3 V of supply voltage.