A switchable operational amplifier (opamp) is examined in this brief. It is based on a current-mirror opamp with switchable transconductance values. Contrary to switched opamp (SO) and partial SO, it can be used to realize both half-delay and full-delay switched-capacitor integrators. The added circuit design complexity is shown to be minimal. Optimal switching is developed in this brief. It is also shown in this brief that the absolute average power consumption can be less as compared with an SO design. The experimental results of a delta-sigma modulator prototype (designed in 1-V 65-nm CMOS), employing the designated switchable-opamp technique, show power reduction without any degradation in SNDR (58.5 dB) or SFDR (67 dB).