Novel voltage-mode biquad without external passive elements

This paper introduces a voltage-mode biquad filter using only active devices such as operational amplifiers and operational transconductance amplifiers (OTAs). The circuit configuration is obtained from Soderstrand's active-R state variable filter as a prototype. The proposed circuit can realize five different biquad transfer functions, and the circuit characteristics can be electronically tuned by adjusting the transconductance gains of the OTAs. An example is given, together with simulated results by PSPICE. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.     

Electronically tunable current-mode active-only biquadratic filter

This paper presents a realization of current-mode active-only filter. The proposed filter is constructed employing operational amplifiers and operational transconductance amplifiers (OTAs). The circuit can realize biquadratic transfer function, and the circuit characteristics can be electronically tuned through adjusting the transconductance gains of the OTAs. An example is given together with simulated result by PSPICE. The circuit configuration is very suitable for implementation in both bipolar or CMOS technologies.     

Novel current-mode active-only biquad with loss-less and lossy integrators

This paper presents a realization of a current-mode active-only biquad with a two-integrator loop structure. The proposed circuit is constructed solely with operational amplifiers (OAs) and operational transconductance amplifiers (OTAs). The circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions, and the circuit characteristics can be electronically tuned by adjusting the transconductance gains of the OTAs. An example is given together with simulated results by PSPICE. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.     

Voltage-mode active-only biquad

This paper presents a realization of a voltage-mode active-only biquadratic circuit. The proposed circuit is constructed employing solely operational amplifiers and operational transconductance amplifiers (OTAs). The circuit configuration is obtained from a second-order structure with two integrator loops. The circuit can realize low-pass, band-pass, high-pass, band-stop, low-pass notch, high-pass notch and all-pass transfer functions by suitably choosing the input and output terminals, and the circuit characteristics can be electronically tuned through adjusting the transconductance gains of OTAs. Some examples are given together with simulated results by PSPICE. The circuit configuration is very suitable for implementation in both bipolar or CMOS technologies.     

Versatile active-only biquad circuits with loss-less and lossy integrators

This paper presents a realization of voltage-mode and current-mode active-only biquad circuits with a two-integrator loop-structure. The circuits are constructed solely with operational amplifiers (OAs) and operational transconductance amplifiers (OTAs). The biquad circuits can realize the multiple circuit transfer functions, and the circuit parameters can be tuned orthogonally through adjusting the transconductance gains of the OTAs. Also, these biquad circuits enjoy very low sensitivities with respect to the circuit active elements. Some examples are given together with simulated results by PSPICE.

The circuit configurations are very suitable for implementation on both bipolar and CMOS technologies.     

电流模式n阶传输函数的OA-OTA实现

提出了一种新的实现任意 n阶电流模式传输函数的网络结构。该电路仅含运算放大器 (OA)和运算跨导放大器 (OTA)有源器件 ,因而适于全集成。适当设置 OTA的跨导值能实现任意高阶传输函数 ,且传输函数的系数可独立调整。文中推导了滤波器的设计公式 ,并给出了截止频率为 1 0 0 k Hz的三阶巴特沃斯低通滤波器实例 ,PSPICE仿真结果表明所提电路及设计公式是正确的     

Current-mode biquad using OTAs and CF

A novel current-mode biquad using operational transconductance amplifiers (OTAs) and current follower (CF) is presented. The circuit can realise lowpass, bandpass, highpass, band-stop and all-pass transfer functions without any circuit matching conditions. The circuit parameters can also be tuned independently by the transconductance gains of the OTAs. The proposed biquad enjoys very low sensitivities with respect to the circuit elements.     

Novel grounded and floating high order immittance simulators using OTAs and OAs

This paper proposes novel grounded and floating high order series and parallel immittance simulators using operational transconductance amplifiers (OTAs) and operational amplifiers (OAs) with a finite gain–bandwidth (GB) product. They are composed of active devices (OTAs and OAs) and resistances, and are suitable for monolithic implementation in either CMOS or bipolar technologies. They also realize both positive and negative high order immittances. The circuit characteristics can be electronically tuned by adjusting the transconductances of OTAs and the GB products of OAs. Any transfer functions are realizable using the proposed simulators. Two examples are shown, together with simulation results.     

OTA-Based Sine-to-Triangular Wave Converter

A sine-to-triangular wave converter based on operational transconductance amplifiers (OTAs) is proposed in this paper. The realization method exploits a hyperbolic tangent behavior of an OTA to convert from a sine wave to a triangular wave. The proposed circuit provides a simple configuration and employs only OTAs as the active elements. This scheme can be operated in both a voltage-controlled mode and a current-controlled mode. The performances of the proposed circuit are discussed in detail and confirmed by the experimental results.     

Universal three input and one output current-mode filter withoutexternal passive elements

A new current-mode universal filter is proposed. The filter uses only operational amplifiers and operational transconductance amplifiers (OTAs) and can realise lowpass, highpass, bandpass, notch and allpass responses without changing circuit topology. The parameters ω₀, ω₀/Q₀, and the gain can be electronically tuned by adjusting the bias currents of the OTAs. The proposed circuit has low sensitivity     

Electronically tunable OTA-C mutually coupled circuit

A novel method for realising a mutually coupled circuit using operational transconductance amplifiers (OTAs) as active elements is proposed. The realised circuit is composed of eight OTAs and two grounded capacitors, and the values of a primary selfinductance, a secondary selfinductance and a mutual inductance can be independently tuned through the bias currents of the OTAs.<>     

High input impedance voltage-mode universal biquadratic filter using two OTAs and one CCII

A three-input and single-output voltage-mode universal biquadratic filter with high input impedance, using only two operational transconductance amplifiers (OTAs), one plus-type second-generation current conveyor (CCII) and two capacitors, is presented. The proposed circuit can realize all the standard filter responses, that is, highpass, bandpass, lowpass, notch and allpass filters, from the same configuration. The proposed circuit has no requirements for component matching conditions.     

Simple square-rooting circuit using OTAs

A method to implement a square-rooting circuit is described. The proposed circuit employs operational transconductance amplifiers (OTAs) as the only active elements. The implementation technique is based on an electronically variable resistor formed by the OTA, where the magnitude of the resistance is controlled by the output current, to provide the square-rooting function. The proposed scheme can operate with both a voltage input and a current input signal. The purpose of the circuit is emphasised in terms of simple configuration, high accuracy and low cost. Experimental results showing the circuit performance are presented.     

Instrumentation amplifiers using operational transconductance amplifiers

Instrumentation amplifier circuits using operational transconductance amplifiers (OTAs) as active circuit elements are proposed in this paper. Two new instrumentation amplifier circuits have been described and experimentally verified, where the first circuit comprises four OTAs and five resistors and the second circuit comprises two OTAs and three resistors.     

Electronically tunable voltage-mode universal filter with single-input five-output using simple OTAs

This article presents a new electronically tunable voltage-mode universal biquadratic filter with single-input five-output using simple operational transconductance amplifiers (OTAs) and grounded capacitors. The proposed configuration provides low-pass, band-pass, high-pass, band-stop and all-pass voltage responses at a high-impedance input terminal that enables easy cascading in voltage-mode. The natural frequency and the quality factor can be set orthogonally by adjusting the circuit components. The natural frequency can also be controlled electronically by adjusting the bias currents of the OTAs. For realising all the five standard filtering functions, no critical-matching conditions are imposed and all the incremental parameter sensitivities are low. Experimental and simulation results that confirm the theoretical predictions are given.     

一种新颖的OTA结构的数模转换器

介绍了一种新颖结构的数模转换器，此转换器的设计核心是采用跨导运算技术，由CMOS运算跨导放大器（OTA）构成。此D／A转换器以模拟电流作为主要信号变量，以跨导运算放大器取代电压运算放大器，以基于OTA的有源元件取代部分无源元件，通过改变OTA的偏置电流，从而改变其互导增益gm和电压放大器增益Au，更适合于IC的集成。采用9个OTA构成一个8位的加法电路，8个OTA的互导增益gm对应8位的数字信号，8个MOS管作为开关运用由8位的数字信号控制，从而实现数字信号到模拟信号的转换。     

OTA-R Schmitt trigger with independently controllable threshold andoutput voltage levels

A current-controllable Schmitt trigger using operational transconductance amplifiers (OTAs) is presented. It consists of two OTAs and two grounded resistors. The output level of the circuit is determined by one OTA and one resistor. And the threshold level is determined by the other OTA and resistor. The theory of operation is presented and experimental results are used to verify theoretical predictions     

Multiple-Mode OTA-C Universal Biquad Filters

Two new multiple-mode (including voltage, current, transconductance, and transresistance modes) OTA-C universal biquad filters are proposed. The first proposed circuit uses only four operational transconductance amplifiers (OTAs) and two grounded capacitors. The second proposed circuit uses five OTAs and two grounded capacitors. Both the proposed circuits can realize voltage, current, transconductance, and transresistance mode universal filtering responses (low-pass, high-pass, band-pass, notch, and all-pass) from the same topology. The first proposed circuit uses the least number of components. This represents an attractive feature from a chip area and power consumption point of view. The second proposed circuit has no need of extra inverting and non-inverting amplifiers for special input signals. Moreover, both the proposed biquads still have (i) the employment of two grounded capacitors, (ii) cascadable connection of the former voltage-mode stage and the latter current-mode stage, and (iii) low sensitivity performance. H-SPICE simulation results confirm the theoretical analysis.     

Novel multiple function analog filter structures and a dual-mode multifunction filter

This paper reports three multi-function filters each of which realizes at least three basic functions without any external passive elements. Depending on the circuit, from one to four operational transconductance amplifiers (OTAs), and two operational amplifiers (OPAMPs) are employed. All three circuits are transimpedance-mode circuits; one of them can also operate as a current-mode filter. Therefore this filter represents a dual-mode, multifunction filter. The presented theory is verified with macro models in simulation program with integrated circuit emphasis (SPICE) simulations and post layout simulations, which are carried out with parasitics extracted from the layouts of the filter chips.     

The realization of high-order OTA-C filter

A new high-order OTA-C active filter using operational transconductance amplifiers (OTAs) and capacitors is presented. The filter has low sensitivity performance and high cut-off frequencies. Its cut-off frequencies can be controlled by a DC voltage or current. In addition, this filter is suitable for integration. Experimental results are given to show its feasibility.