A +100dB gain, rail-to-rail output, low distortion, low noise amplifier in BiCMOS technology

This paper describes a rail to rail output low noise, highly linear operational amplifier implemented in 0.5 mum BiCMOS technology. A novel gain boosting technique applied to a folded cascode input stage allows a low frequency gain of over 100 dB to be achieved with a two stage design, while additionally allowing the input to sense common mode ground. The disadvantage incurred in the relatively high DC current consumption of the folded cascode input stage is somewhat mitigated by a novel interstage coupling technique allowing bias current to be shared. Two further distortion reducing features of the output stage are the compensation technique and the presence of complementary emitter followers.