Active filter design using operational transconductance amplifiers: A tutorial
TL;DR: In this paper, the operational transconductance amplifier (OTA) is used in voltage-controlled amplifiers, filters, and impedances for continuous-time monolithic filters, where the total number of components used in these circuits is small, and the design equations and voltage-control characteristics are attractive.
Abstract: Basic properties of the operational transconductance amplifier (OTA) are discussed. Applications of the OTA in voltage-controlled amplifiers, filters, and impedances are presented. A versatile family of voltage-controlled filter sections suitable for systematic design requirements is described. The total number of components used in these circuits is small, and the design equations and voltage-control characteristics are attractive. Limitations as well as practical considerations of OTA-based filters using commercially available bipolar OTAs are discussed. Applications of OTAs in continuous-time monolithic filters are considered.
Citations
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TL;DR: In this article, two basic implementations for current-controlled first-order transfer functions, operating either in voltage-mode or in current-mode, are described, which require one or two of the preceding controlled conveyors and use capacitors only.
Abstract: When the mixed translinear loop is used in a voltage follower implementation the value of its output resistance depends on its bias current. This property is used in the realization of a current controlled conveyor (CCCII), which has therefore its serial resistance on port X controlled by the bias current. The two basic implementations, that allow from a CCCII and without additive resistances to realize controlled voltage-current converters, are described. A current-controlled voltage-amplifier and a current-controlled current-amplifier are then analyzed. They are implemented from only two CCCIIs and do not require any passive component. The principal implementations for current controlled first-order transfer functions, operating either in voltage-mode or in current-mode, are introduced. They require one or two of the preceding controlled conveyors and use capacitors only. SPICE simulation results, obtained using the parameters of the HF3CMOS process from SGS THOMSON, are given for the CCCII and for its main applications. They confirm the validity of the theoretical analyzes and also underline the high frequency potential of the current controlled implementations introduced. A second-order bandpass filter, operating in voltage-mode, is also described. It is obtained from CCCIIs and two capacitors only. Its centre frequency, which is adjustable by acting on the control currents of the conveyors, is equal to 11.3 MHz for I/sub 0/=20 /spl mu/A and to 16.6 MHz for I/sub 0/=30 /spl mu/A. This variation produces very small changes in both the quality factor and the gain (variations less than 7%). Comparisons between existing OTA circuits and the ones implemented from controlled conveyors, are also given. They underline the advantage which result from implementations using controlled conveyors.
508 citations
01 Feb 2000
TL;DR: In this article, an updated version of a 1985 tutorial paper on active filters using operational transconductance amplifiers (OTAs) is presented, and the integrated circuit issues involved in active filters (using CMOS transconductances amplifiers) and the progress in this field in the last 15 years is addressed.
Abstract: An updated version of a 1985 tutorial paper on active filters using operational transconductance amplifiers (OTAs) is presented. The integrated circuit issues involved in active filters (using CMOS transconductance amplifiers) and the progress in this field in the last 15 years is addressed. CMOS transconductance amplifiers, nonlinearised and linearised, as well as frequency limitations and dynamic range considerations are reviewed. OTA-C filter architectures, current-mode filters, and other potential applications of transconductance amplifiers are discussed.
343 citations
TL;DR: In this paper, a direct block diagram approach is used to generate two integrator loop filter structures using operational transconductance amplifiers (OTAs) and capacitors (TAC).
Abstract: Generation of two integrator loop filter structures using operational transconductance amplifiers (OTAs) and capacitors (TAC) is presented. A direct block diagram approach is used to generate the TAC filter structures. The basic filter building blocks consist of a lossless integrator, lossy integrators and the three types of summers. They are implemented using OTAs as the active components. The resulting TAC second-order filter structures, some previously reported and others new structures, are generated in an orderly way. It is shown that the selection of the best structure depends on the particular application or design specifications. The generated TAC biquadratic structures are only very suitable for monolithic filters since typically only OTAs and two capacitors are needed. A TAC filter structure homologous to the conventional KHN op amp filter structure is presented. Programmability of omega /sub p/, Q/sub p/ and voltage gain is considered. >
256 citations
TL;DR: In this paper, a 5-V, 7-order elliptic analog magnitude filter for antialiasing in digital video applications is described, based on a G/sub m/-C technique, exhibits a dynamic range of 61 dB and dissipates a power of 75 mW.
Abstract: An approach that has made possible the integration of video frequency continuous-time filters with wide dynamic range is discussed. The tuning scheme necessary to maintain the stable and accurate frequency response in the presence of temperature variations, process tolerance, and aging is described. Detailed design techniques specific to high-frequency operation are introduced to implement a 5-V, seventh-order elliptic analog magnitude filter for antialiasing in digital video applications. The filter, based on a G/sub m/-C technique, exhibits a dynamic range of 61 dB and dissipates a power of 75 mW. Ninety-two chips from various wafers and two different process runs were tested. Seventy-five percent of the fabricated chips were functional, and 63% of them met the commercial-grade specifications in spite of an error in the layout which forced the phase control circuitry to perform suboptimally. >
208 citations
TL;DR: In this paper, a unified, comprehensive approach to the design of continuous-time and discrete-time cellular neural networks (CNNs) using CMOS current-mode analog techniques is presented.
Abstract: A unified, comprehensive approach to the design of continuous-time (CT) and discrete-time (DT) cellular neural networks (CNNs) using CMOS current-mode analog techniques is presented. The net input signals are currents instead of voltages, which avoids the need for current-to-voltage dedicated interfaces in image processing tasks with photosensor devices. Outputs may be either currents or voltages. Cell design relies on exploiting current mirror properties for the efficient implementation of both linear and nonlinear analog operators. Basic design issues, the influence of nonidealities and advanced circuit design issues, and design for manufacturability considerations associated with statistical analysis are discussed. Experimental results are given for three prototypes designed for 1.6- mu m n-well CMOS technologies. One is discrete-time and can be reconfigured via local logic for noise removal, feature extraction (borders and edges), shadow detection, hole filling, and connected component detection (CCD) on a rectangular grid with unity neighborhood radius. The other two prototypes are continuous-time and fixed template: one for CCD and other for noise removal. >
192 citations
References
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TL;DR: Fully integrated, high-frequency continuous-time filters can be realized in MOS technology using a frequency-locking approach to stabilize the time constants using a phase-locked loop.
Abstract: Fully integrated, high-frequency continuous-time filters can be realized in MOS technology using a frequency-locking approach to stabilize the time constants. A simple, fully differential integrator, optimized for phase-error cancellation, forms the basic element; a complete filter consists of intercoupled integrators. The center frequency of the filter is locked to an external reference frequency by a phase-locked loop. A prototype sixth-order bandpass filter with a center frequency of 500 kHz dissipates 55 mW and occupies 4 mm/SUP 2/ in a 6-/spl mu/m CMOS technology.
403 citations
TL;DR: In this paper, some novel circuit techniques for realizing linear CMOS tranconductance elements are proposed, which have superior linearity and input voltage range compared with the conventional source-coupled differential pair.
Abstract: Some novel circuit techniques for realizing linear CMOS tranconductance elements are proposed. The circuits discussed have superior linearity and input voltage range compared with the conventional source-coupled differential pair. Design tradeoffs are examined and computer simulation results are used to verify theoretical predictions. The results show close agreement between predicted behavior and simulated performance.
343 citations
TL;DR: In this paper, two transconductance amplifiers are presented in which the concept of an input dependent bias current has been introduced, and the amplifiers combine a very low standby power dissipation with a high driving capability.
Abstract: Two transconductance amplifiers are presented in which the concept of an input dependent bias current has been introduced. As a result, these amplifiers combine a very low standby power dissipation with a high driving capability. The first amplifier, suited for SC filters, is fairly small (0.075 mm/SUP 2/) and has a slew rate which is more than an order of magnitude better than micropower amplifiers presented earlier. The second amplifier can be used as a micropower buffer. Nearly the whole supply current is used to charge the load capacitor so that this amplifier has a high efficiency.
284 citations
01 Jan 1978
TL;DR: In this paper, a new approach for realizing high-order analog filters which can be fully integrated using a compatible bipolar and ion-implanted JFET process is described, which is based on the recognition that what is really needed is a long time constant monolithic integrator.
Abstract: A new approach for realizing high-order analog filters which can be fully integrated using a compatible bipolar and ion-implanted JFET process is described. This approach is based on the recognition that what is really needed is a long time constant monolithic integrator which can be effectively realized in a small silicon area. These integrators have been designed, fabricated, and used in a `leapfrog' or active ladder configuration to realize a fifth-order 8 kHz Chebyshev low-pass filter with 0.1 dB passband ripple. No external trimming operations and no anti-aliasing prefilter are required.
113 citations
01 Dec 1980
TL;DR: In this article, a single-chip gyrator filter for separating the components of the video signal in a TV receiver is described which is suitable for mass production in a standard bipolar process (f/SUB T//spl ap/400 MHz).
Abstract: A single-chip gyrator filter for separating the components of the video signal in a TV receiver is described which is suitable for mass production in a standard bipolar process (f/SUB T//spl ap/400 MHz). The 11 mm/SUP 2/ filter chip operates at frequencies up to 10 MHz, requires no tuning or alignment and has Q-factors which are stable with temperature. The IC contains an automatic tuning system which tunes the five resonators of the filter by aligning an auxiliary gyrator resonator with the crystal oscillator present in the color decoder of a TV receiver. Problems of matching the frequencies of the individual gyrator resonators are discussed, showing how alignment accuracy of 0.5 percent can be obtained when resistivities and specific capacitances have production spreads of at least 10 percent. Various gyrator circuit configurations are given which minimize the circuit complexity and, hence, the chip area. Computer aided design techniques for the filter using geometrically scaled models and macromodeling are presented and it is shown how a complete simulation of the chip led to a significant improvement in bandstop performance. Finally, the measured responses are presented and the filter performance is discussed in the light of present-day requirements.
106 citations