Subthreshold DC‐gain enhancement by exploiting small size effects of MOSFETs

A pseudo‐cascode split‐transistor technique is proposed for DC‐gain enhancement of amplifiers in the subthreshold by exploiting the small size effects of metal–oxide semiconductor field effect transistors (MOSFETs) including the reverse short‐channel effect and the inverse narrow‐width effect. It requires no body‐biasing and occupies a small area. A compact 114 μm 2 two‐stage amplifier with pseudo‐cascode compensation for in‐pixel amplification in vision sensors has been designed using the proposed technique. A total of 10 samples of split‐transistors and amplifiers fabricated in an UMC 0.18 μm standard CMOS process were measured. More than half of the tested split‐transistors show considerable DC‐gain enhancement over a wide range of bias currents and nine amplifiers have increased DC gains larger than 85 dB at about 4 nA power consumption.