In this paper a low-voltage two-stage Op Amp is presented. The Op Amp features rail-to-rail operation and has an @put stage with a constant transconductance (%) over the entire common-mode input range. The input stage consists of an n- and a PMOS differential pair connected in parallel. The constant gm is accomplished by regulating the tail-currents with the aid of an MOS translinear (MTL) circuit. The resulting gn is constant within 5% The common-source output stage employs a feedback circuit which also contains an MTL circuit. This feedback circuit ensures class AB operation and prevents the transistors in the output stage from cutting off. The Op Amp will be realized in a semi custom CMOS process with minimum channel lengths of 1Opm. Simulations show that the minimum supply voltage is less than 2.5 V. A unity gain bandwidth of 550 kHz and a DC voltage gain larger than 80 dB are feasible. The input range exceeds the supply rails, whereas the output range reaches the rails within 130 mV.
|Title of host publication||Proceedings International Symposium on Ciruits and Systems (ISCAS '93)|
|Place of Publication||Chicago-Illinois|
|Publication status||Published - 3 May 1993|
Botma, J. H., Wassenaar, R. F., & Wiegerink, R. J. (1993). A low-voltage Op Amp with rail-to-rail constant-gm input stage and a class AB rail-to-rail output stage. In Proceedings International Symposium on Ciruits and Systems (ISCAS '93) (pp. 1314-1317). Chicago-Illinois: IEEE. https://doi.org/10.1109/ISCAS.1993.393972