Dual Output Operational Transconductance Amplifiers Research Articles

300 mA LDO Using 0.94 μA IQ With an Additional Feedback Path for Buffer Turn-off Under Light-Load Conditions

This paper proposes a 300 mA low-dropout (LDO) regulator using an $I_{Q}$ of only $0.94~\mu \text{A}$ , which has the advantage of minimizing power consumption in the standby mode of a battery-based system. The LDO uses a source follower buffer with dynamic biasing to maintain loop stability and load transient response performance. Under light-load conditions, the buffer enters a fully-off state because there is a sub-nA bias current. Therefore, the LDO uses a dual output operational transconductance amplifier (DO-OTA) for operation under light-load conditions. The second output of the DO-OTA for light-load operation in the LDO forms an additional feedback path instead of the fully-off buffer. The second output of the DO-OTA is designed to consume a current lower than the bias current of the buffer while operating. Furthermore, the buffer in the LDO is designed for operation above 5 mA $I_{L}$ . While the buffer is operating, the dynamic biasing current of the buffer is used as the second output of the DO-OTA. The second output of the DO-OTA has lower output impedance characteristics than its main output, so the LDO can secure loop stability under light-load conditions by lowering the DC gain. As a result, the LDO exhibits load transient response performance up to 300 mA by using a minimal $I_{Q}$ under the no-load condition. The LDO is based on a 180 nm bipolar-CMOS-DMOS (BCDMOS) process and covers an area of approximately $256 \times 143 \mu \text {m}^{2}$ . The measured $I_{Q}$ is $0.94~\mu \text{A}$ under the no-load condition with a maximum load current of 300 mA.

A Simple and Accurate CMOS Sample-and-Hold Circuit Using Dual Output-OTA

A Simple and Accurate CMOS Sample-and-Hold Circuit Using Dual Output-OTA

Versatile Voltage-Mode Biquadratic Filter and Quadrature Oscillator Using Four OTAs and Two Grounded Capacitors

This article presents a versatile voltage-mode (VM) biquad filter with independently electronic tunability. The proposed structure using one dual-output operational transconductance amplifier, three single-output operational transconductance amplifiers (OTAs) and two grounded capacitors was explored to derive a new VM quadrature oscillator with the independent control of the oscillation frequency and the oscillation condition. The proposed versatile VM biquad filter achieves nearly all of the main advantages: (i) simultaneous realizations of band-reject, band-pass, and low-pass from the same architecture, (ii) multiple-input and multiple-output functions, (iii) independent electronic adjustability of quality factor and resonant angular frequency, (iv) no resistor needed, (v) all input terminals with cascade functions, (vi) no additional inverting amplifier for input signals, (vii) using only grounded capacitors, and (viii) easy to implement a VM quadrature oscillator with independent electronically controlled oscillation frequency and oscillation condition. The proposed versatile VM biquad filter employs only four OTAs and two grounded capacitors. The active components of the proposed VM biquad filter are one less than that of recent reports. The proposed circuit also brings versatility and simplicity to the design of VM biquad filters and VM quadrature oscillators. Filters and oscillators with less active and passive components have the advantages of low cost, low power dissipation, low circuit complexity, and low noise. Commercially available integrated circuit LT1228 and discrete components can be used to implement the proposed OTA-based circuits. The simulation and experiment results validated the theoretical analysis.

An electronically controllable, fully floating memristor based on active elements: DO-OTA and DVCC

In this paper, we have presented a Dual-Output Operational Transconductance Amplifier (DO-OTA) and Differential Voltage Current Conveyor (DVCC)-based fully floating emulator which enables the memristor current to flow in both directions when used with other circuit elements. The proposed memristor consists of only one DO-OTA, one DVCC, one grounded capacitor that is attractive for an integrated circuit, and two PMOS transistors operating as an electronic resistor. The proposed fully floating memristor emulator includes two very important features: (1) the fixed and variable memductance parts of the circuit are electronically adjustable, and (2) both incremental and decremental circuit behaviors can be obtained without altering the circuit topology. The circuit was laid using the Cadence Spectre Analog Environment with TSMC 0.18 µm process parameters and occupied a layout area of only 119 µm × 90 µm. The post-layout simulation results for the memristor circuit were obtained for different operating frequencies and all simulations were fully compatible with the experimental memristor behaviors. Finally, the memristor circuit was built on a breadboard using discrete circuit elements, and all experimental results were also compatible with the expected memristor characteristics.

Dual-Output Operational Transconductance Amplifier-Based Electronically Controllable Memristance Simulator Circuit

In this paper, a new floating analog memristance simulator circuit based on dual-output operational transconductance amplifiers (DO-OTA) and passive elements is proposed. Theoretical derivations are presented which describe the circuit characteristics. DO-OTA active elements in the proposed circuit are realized with CMOS transistors, and PSPICE simulations are performed. Also workability of the circuit is tested experimentally by using commercially available integrated circuits. Theoretical derivations are validated with PSPICE simulation and experimental results. All results show that proposed simulator circuit provides frequency-dependent pinched hysteresis loop and nonvolatility feature. Exciting frequency, minimum and maximum memristance values and memristance range can be adjustable electronically with bias currents by changing the transconductances of DO-OTAs. Simulator circuit has a frequency range of 1 Hz–180 kHz.

New OTA-C Current-Mode Second-order and Fourth-Order Band-Pass Filters

In this paper, a general two-admittance current-mode circuit structure using Dual-Output OTA (DO-OTA) is explored to derive new second-order and fourth-order band-pass filters. The proposed second-order band-pass filtercircuits offer advantageous features like ease of design, good sensitivity and orthogonal tunability of pole-Q. The proposed fourth-order band-pass filtercircuit is attractive as it requires less number of OTAs and capacitors.PSPICE simulation results are given for the proposed circuits

Novel First-Order and Second-Order Current-Mode Filters Using Multiple-Output Operational Transconductance Amplifiers

In this paper, a general structure using dual-output operational transconductance amplifiers (OTAs) is explored to derive new first-order and second-order multi-function filters using OTAs with multiple current outputs and with and without grounded capacitors. Two first-order all-pass filters that have been obtained are presented, together with an analysis of nonidealities of OTAs, viz., finite bandwidth and parasitic output and input resistance and capacitance. Second-order multi-function filters obtained by using OTA-C simulated inductances in the proposed general structure are also presented. The realization of quadrature oscillator using the proposed first-order all-pass networks is also considered. Detailed analysis of nonideal frequency performance of the OTAs as well as finite output and input impedances is presented. SPICE simulation results are also given for the proposed circuits.

Voltage-mode universal biquadratic filter with one input and five outputs using OTAs

A new voltage-mode universal biquadratic filter with one input and five outputs is presented. The new circuit uses one triple-output OTA, one dual-output OTA, three single-output OTAs and two grounded capacitors. This circuit offers the following features: high input impedance, realizing all the standard filter functions; lowpass, bandpass, highpass, notch and allpass, simultaneously, orthogonal controllability of ωo and Q, and low active and passive sensitivities.

High-output-impedance CMOS dual-output OTA suitable for wide-range continuous-time filtering applications

A high-output-impedance precision current mirror is implemented in a CMOS dual-output OTA (DOTA) structure by means of an efficient implementation method, which is also applicable to other current-output-based active devices. The new DOTA, when used in a DOTA-C integrator, enables integration at very low frequencies, with a capacitor on the order of several picofarads.

Simulation of Active-only Floating Inductance

A simple circuit for realizing active-only lossless floating inductor is presented. The circuit uses only two active elements ; a dual output operational transconductance amplifier and an internally compensated operational amplifier. The circuit is suitable for monolithic implementation in either bipolar or MOS technologies. Simulation results of a high-order lowpass filter using two simulated lossless floating inductors are included.

Systematic generation of current mode dual-output OTA filters using a building block approach

A synthesis method is described for generating current mode dual-output OTA filter configurations. The procedure is based on a building-block approach and provides a systematic and structural method for generating filter circuits. Using this method, the capabilities of dual-output OTA devices in active filter design can be fully investigated. While the procedure is general, it is shown how filter circuits (lowpass, highpass, band pass and band reject) based on one, two and three dualoutput OTAs are generated.

Current-mode multiple-loop feedback filters using dual-output OTAs and grounded capacitors

A systematic method is presented for the generation, analysis and synthesis of current-mode continuous-time multiple-integrator-loop all-pole filters using dual-output operational transconductance amplifiers and grounded capacitors (DO-OTA-GC). The general theory based on a multiple-loop feedback model is formulated. A number of architectures including canonical realizations are developed, with particular emphasis on high-order configurations. A sensitivity analysis method is also given and parasitic effects on the structures are discussed. The general formulations are verified by direct analysis of the generated individual circuits. Design examples are also presented. © 1997 by John Wiley & Sons Ltd.

Design of current-mode multiple output OTA and capacitor filters

This paper describes a new second-order current-mode filter using dual output operational transconductance amplifiers (DO-OTA) and grounded capacitors. The circuit consists of four DO-OTAs and two grounded capacitors, is of the two integrator loop structures, and realizes the basic LP, BP, HP functions. Generation of universal current-mode filter configurations based on basic current-mode DO-OTA-C filters by using input current distributors and/or output current summers are also discussed.

Structure generation of current-mode two integrator loop dual output-OTA grounded capacitor filters

A variety of new current-mode continuous-time two integrator loop filter architectures incorporating dual output operational transconductance amplifiers (DO-OTA) and capacitors (C) are generated. These DO-OTA-C configurations consist of 2-6 DO-OTAs, depending on the structure and only 2 grounded capacitors. They are convenient for integration, suitable for high frequency, multifunctional, electronically tunable, of low sensitivity, simple in structure and easy to design. The selection of the filter structure and effects of DO-OTA nonidealities are discussed.

Current mode filter structure based on dual output transconductance ampifiers

A new curent mode filter structure based on the dual output OTA is described. By appropriate choice of components, the structure provides lowpass, highpass, and bandpass responses. Experimental results which confirm the theoretical analysis are given.

A current-mode square-rooter in CMOS technology

This paper presents a new current-mode square-rooter which is implemented with a squarer and a dual-output operational transconductance amplifier (OTA). The circuit is offset-free and independent of either the process or the transistor parameters. Simulation results show very high accuracy. The proposed circuit can also be extended to a two-quadrant analog multiplier.