Rt. Wang et R. Harjani, PARTIAL POSITIVE FEEDBACK FOR GAIN ENHANCEMENT OF LOW-POWER CMOS OTAS, Analog integrated circuits and signal processing, 8(1), 1995, pp. 21-35
Four circuit schemes that use partial positive feedback for gain enhan
cement in CMOS OTAs are examined. These circuit schemes are classified
as type I and type II circuits. Type I circuits use a differential in
put pair with positive feedback and type II circuits use a active load
with positive feedback. As the primary emphasis of these circuits is
for micropower operation, the circuits have been examined in detail in
the subthreshold region. A comparison of the primary characteristics
of these circuits together with simulation results are presented. It i
s shown that partial positive feedback is a viable technique to increa
se the gain and the bandwidth of CMOS OTAs. Without any increase in po
wer, a 20 dB increase in gain and a 5X improvement in bandwidth is fea
sible.