Research on Offset Reduction Technique Using Hybrid Mode Servo Method for Amplifiers
宮田 清也 ,
淡野, 公一 ,
田村, 宏樹外山, 貴子
158 , 2016-07-29 , 宮崎大学工学部
This thesis describes offset cancellation technique of CMOS amplifier for biological signal processing LSI. Our labratory try to develop the LSI for s-EMG (surface-Electromyogram). s-EMG has low-frequency and very small signal, so it needs to amplify for signal processing. But offset arises from mismatch caused by process variations, and it is very difficult to discriminate between s-EMG and offset. Thus biological signal processing LSI needs offset cancellation circuit to attenuate offset infection. DC servo circuit is one of the offset cancellation circuit. But DC servo circuit needs large passive component's value for low-frequency signal such as s-EMG. This causes an obstruction to integrate each circuit of biological signal processing LSI into one chip. To solve this problem, I propose hybrid mode servo circuit. This circuit's cut-off frequency (fc) can be lower by reducing transconductance (gm) of OTA used in integrator and increasing attenuation rate of attenuator. So this circuit can cancel offset without large passive component's value for low-frequency signal. The performance of the proposed circuit is evaluated through HSPICE simulation with 0.6μm CMOS device parameters. The simulation results are reported in this thesis.