A 0.6 V class‐AB rail‐to‐rail CMOS OTA exploiting threshold lowering

Abstract

A class-AB OTA (operational transconductance amplifier) topology with rail-to-rail input common-mode range is proposed for application in very low-voltage applications. High efficiency is achieved by reusing transistors both for class-AB operation and for mirroring the output currents, and a threshold lowering technique is applied to allow supply voltages less than two threshold voltages. Simulations in 40 nm CMOS technology show 41 dB gain at ±0.3 V supply voltage, a unity-gain frequency of 8.8 MHz on a 5 pF load, class-AB behaviour and full rail-to-rail operation when closed in unity-gain buffer configuration.

0.6‐V CMOS cascode OTA with complementary gate‐driven gain‐boosting and forward body bias

“…The OTA input stage is an NMOS differential pair with a replica control loop for the biasing current and is shown in Figure 5. 10 These devices are biased in the subthreshold. Forward body bias has again been exploited to reduce the threshold voltage of the input devices M23 and M24 by connecting the body of the input devices to V DD .…”

“…This result can be achieved by exploiting transistors with different threshold voltages (which are now available in all advanced CMOS processes) or using a suitable body bias to lower the value of the threshold voltage of M2, as shown in Figure 2, through bias voltage VB. 10,11 The maximum voltage that can be applied to the body of M2 is limited by the body-source junction that has to remain reverse biased. This is however not a concern for very low-voltage applications.…”

“…Forward body bias has again been exploited to reduce the threshold voltage of the input devices M23 and M24 by connecting the body of the input devices to V DD . 10 These devices are biased in the subthreshold.…”

A gm/ID-Based Design Strategy for IoT and Ultra-Low-Power OTAs with Fast-Settling and Large Capacitive Loads

“…In particular, the reduction in the MOSFET intrinsic gain (g m r d ∼ 10), in the dynamicrange and in the signal-to-noise ratio can severely affect the circuit performance [11][12][13][14][15][16][17][18].…”

84 dB DC‐gain two‐stage class‐AB OTA

“…The requirement of portability places some restrictions on the size, weight, and power of the IC. The operational trans-conductance amplifier (OTA) is one of the most widely used building blocks in analog design [1][2][3][4][5][6][7][8]. OTA can be used in low-voltage, low-power, and high-speed applications such as continuous-time Gm-C filters, switched-capacitor circuits, data converters, biomedical implants, signal conditioning of sensors, voltage regulators, and RF receivers [9][10][11][12][13][14][15][16][17][18][19][20].…”