A 1 V low-power low-noise DTMOS based class AB opamp

In this paper, the authors described a novel class AB opamp based on dynamic threshold voltage transistors (DTMOS) for low voltage (1-V), low power and low noise applications. The opamp is used to build the front-end receiver part of a near infrared spectroreflectometry (NIRS) device. The opamp has a two-stage configuration; DTMOS pseudo pMOS differential input pairs are used for input common-mode range enhancement, followed by a single ended class AB output. Experimental measurements from previous designs confirm the usage of a DTMOS device to build a 1-V opamp, using standard 0.18-μm CMOS technology. The performed post-layout simulation results show an input referred noise of 107 nV/√Hz at 1 kHz, and a power consumption of 33.1 μW under 5 pF and 10 kΩ loads. The dc open loop gain is 60 dB, and a unity frequency of 2.73 MHz. The opamp has a CMRR of 100 dB, and input and output swings of 0.6 V and 0.8 V respectively.