A 0.8‐V supply bulk‐driven operational transconductance amplifier and Gm‐C filter in 0.18 µm CMOS process

Abstract

SUMMARYA low voltage bulk-driven operational transconductance amplifier (OTA) and its application to implement a tunable Gm-C filter are presented. The linearity of the proposed OTA is achieved by nonlinear terms cancelation technique, using two paralleled differential topologies with opposite signs in the third-order harmonic distortion term of the differential output current. The proposed OTA uses 0.8 V supply voltage and consumes 31.2 μW. The proposed OTA shows a total harmonic distortion of better than À40 dB over the tuning range of the transconductance, by applying 800 mV ppd sine wave input signal with 1 MHz frequency. The OTA has been used to implement a third-order low-pass Gm-C filter, which can be used for wireless sensor network applications. The filter can operate as the channel select filter and variable gain amplifier, simultaneously. The gain of the filter can be tuned from À1 to 23 dB, which results in power consumptions of 187.2 to 450.6 μW, respectively. The proposed OTA and filter have been simulated in a 0.18 μm CMOS technology. Simulations of process corners and temperature variations are also included in the paper.

A 63‐dB gain OTA operating in subthreshold with 20‐nW power consumption

“…Another important application of the OTAs is integrated filters which need high linearity and low input referred noise . Decreasing power supply leads to the input voltage range degeneration and consequently worse linearity that can be solved using bulk‐driven technique.…”

Biasing technique to improve total harmonic distortion in an ultra‐low‐power operational transconductance amplifier

“…An extension of the results of the gate-driven differential pair can be used to design a bulk-driven differential pair. Knowing that the output current in bulk-driven differential pair is given by (18), the linear range increases in 1/(n p − 1). bias current in both topologies, gate-driven and bulk-driven, are the same.…”

“…Several techniques about increasing the linear range [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have been proposed in the literature, based on source generation, adaptive biasing, pseudo-differential stages, cross-coupling, multiple differential pairs, current cancellation, and the combination of some of them. Other technique is the use of bulkdriven differential pair to enhance the linear range of OTA [3,4,[11][12][13].…”

±0.18‐V supply voltage gate‐driven PGA with 0.7‐Hz to 2‐kHz constant bandwidth and 0.15‐μW power dissipation

“…Most of them are bulk-driven (BD) circuits based on injecting input signals through the bulk terminal while connecting the gate to a supply rail [1][2][3][4][5][6][7] . For analog circuits based on op-amps, this can be achieved by keeping both amplifier input terminals close to a supply rail.…”

“…Several papers have reported systems operating from supplies as low as 0.5 V (some without experimental verification). Most of them are bulk-driven (BD) circuits based on injecting input signals through the bulk terminal while connecting the gate to a supply rail [1][2][3][4][5][6][7] . The main disadvantage of the BD technique is that bulk transconductance is usually a factor 4-5 lower than the gate transconductance.…”