A highly linear bulk-driven CMOS OTA for continuous-time filters

Abstract

In this paper we present a bulk-driven CMOS triode-based fully balanced operational transconductance amplifier (OTA) and its application to continuous-time filters. The proposed OTA is linearly tunable with the feature of low distortion and high output impedance. It can achieve wide input range without compromising large transconductance tuning interval. Using a 0.18 lm n-well CMOS process, we have implemented a third-order elliptic low-pass filter based on the proposed OTA. Both the simulation and measurement results are reported. The total harmonic distortion is more than -45 dB for fully differential input signals of up to 0.8 V peak-peak voltage. A dynamic range of 45 dB is obtained under the OTA noise integrated over 1 MHz.

Sub-Volt Fully Balanced Differential Difference Amplifier

“…In order to overcome the reduction of the supply voltage and the high value of the threshold voltage, some new techniques have been presented in the literature e.g.,°oating-gate (FG), quasi-°oating-gate (QFG) and bulk-driven (BD) techniques. [46][47][48][49][50] Based on these techniques many interesting circuits were designed and published in the literature, such as voltage followers (VF), 6,7 operational ampli¯ers (Op-Amps), 8,9,47 operational transconductance ampli¯ers (OTAs), [10][11][12][13][14][15][16][17][18][48][49][50] second generation current conveyors (CCIIs), [19][20][21][22][23][24] current feedback ampli¯ers (CFAs), 19 current di®erencing transconductance ampli¯ers (CDeTAs), 26 di®erential-input bu®ered and external transconductance ampli¯ers (DBeTAs), 27 current mirrors (CMs), 28,29 di®erential voltage current conveyors (DVCCs), 30,31 di®erential di®erence current conveyors (DDCCs), 32 winner-take-all (WTAs) circuits, 33 bulk-controlled sub-threshold MOS resistors, 50 and others.…”

0.5‐V bulk‐driven OTA and its applications

“…One of the techniques which could facilitate the design of ultra‐low‐voltage OTAs and op‐amps is based on the application of bulk‐driven MOSFETs . In such solutions, the bulk terminal is used as an input rather than the gate.…”

A novel OTA with digitally controlled and linearly tunable transconductance

“…There have been several approaches to designing linearly tunable OTA based on MOS transistors operating in saturation region [3]. However, most of them operate in voltage-controlled mode, and the controllable voltage ranges are rather limited, so do the linear transconductance ranges [4]. A current-controlled OTA was presented in [5], but the linearly tunable range is narrow because the MOS transistors are working in the weak-inversion region.…”