NOISE ANALYSIS IN A 0.8 V FORWARD BODY-BIAS CMOS OP-AMP DESIGN

Noise model of a MOSFET, which includes the effect of forward-body bias, is proposed. Thermal noise and shot noise are extracted and their variations with the forward body-bias are compared. It is found that the shot noise increases with the forward body-bias and becomes significant above 0.4 V forward bias. A CMOS op-amp is designed utilizing forward body-bias technique combined with a level shift current mirror. The designed amplifier dissipates power of 40 μW and operates at ± 0.4 V to achieve a gain of 77 dB. The noise in this ultra low-power op-amp is also investigated. The total simulated output noise density of 320×10-12 V 2/ Hz in the ultra-low power op-amp design is slightly lower than the calculated 413×10-12 V 2/ Hz value from the proposed model.