Quasi Rail-to-Rail Very Low-Voltage OPAMP With a Single pMOS Input Differential Pair

In this brief, a quasi-rail-to-rail low-voltage operational amplifier (V
_DD
-V
_SS
-V
_DSATP
-V
_DSATN
) is introduced. A common-mode adapter that uses the common-mode voltage present at the common-source node of the available differential pair to accommodate the large common-mode input signal is proposed. The common-mode adapter operates properly at 300 kHz while driving a load capacitor of 15 pF and employs only 95 muW of static power. The amplifier was fabricated in a standard AMI 0.5-mum CMOS process (V
_tn
=0.7 V and Vtp=-0.9 V) and achieves an IM3 of - 48 dB at 300 kHz for a two-tone input signal of 0.8 V
_pk-pk
. A 1-V total supply voltage was used