High-Performance Three-Stage Single-Miller CMOS OTA With No Upper Limit of ${C}_{L}$

This brief presents a low-power, area-efficient three-stage CMOS operational transconductance amplifier (OTA) suitable for very large capacitive loads, C
_L
. A single Miller capacitor and an inverting current buffer embedded in the input stage are exploited to implement the frequency compensation network. An additional feed-forward path and a slew rate enhancer are also utilized to improve the large-signal transient response. Detailed small-signal analysis reveals that the proposed OTA does not exhibit an upper limit of drivable C
_L
. The OTA is fabricated in a standard 0.35-μm technology and occupies 0.0027 mm
²
of die area. Under 1.4-V supply and 6.36-μA quiescent current consumption, it provides a dc gain greater than 110 dB and is stable for any C
_L
larger than 5 nF. Comparison with the state of the art shows remarkable improvement of both small- and large-signal performance.