In the paper, an analysis of the state-of-the-art of active elements for analog signal processing is presented which support - in contrast to the conven tional operational amplifiers - not only the voltage-mode but also the current- and mixed-mode operations. Several pro blems are addressed which are associated with the utiliza tion of these elements in linear applications, particularly in frequency filters. A methodology is proposed which generates a number of fundamentally new active elem ents with their potential utilization in various areas o f signal processing.

Active Elements for Analog Signal Processing: Classification, Review, and New Proposals

In this paper, a new CMOS high-performance electronically tunable second-generation current conveyor (ECCII) is presented. The current gain of the proposed ECCII can be controlled electronically by adjusting the ratio of dc bias currents of the ECCII. The output terminal of the proposed ECCII has high impedance, which enables easy cascadability. Also, as an application, the proposed ECCII is used for realizing a universal current-mode filter. The filter realizes low-pass, bandpass, and high-pass responses simultaneously. The low-pass response is obtained at high impedance output and its gain can be independently tuned by changing the current gain of the relevant CC. SPICE simulation results using TSMC 0.35-/spl mu/m CMOS process model shows excellent performance for the proposed ECCII. The proposed circuit consumes average power of 6.6 mW using /spl plusmn/1.5-V supply voltages.

A new CMOS electronically tunable current conveyor and its application to current-mode filters

This article presents a basic current-mode building block for analog signal processing, namely current controlled current conveyor transconductance amplifier (CCCCTA). Its parasitic resistance at current input port can be controlled by an input bias current. It is very suitable for use in current-mode signal processing, which is becoming more popular than voltage mode. The proposed element is realized in a bipolar technology and the performances are examined through PSPICE simulations, displaying usabilities of the new active element. The CCCCTA performs tuning over a wide current range. The description includes some examples as a current-mode universal biquad filter, voltage-mode universal biquad filter, a grounded inductance simulator, a current-mode multiplier/divider and an oscillator. They occupy only a single CCCCTA.

Current controlled current conveyor transconductance amplifier (CCCCTA): a building block for analog signal processing

A multiphase sinusoidal oscillator circuit is presented. The oscillator can produce N output-currents (N being even or odd) equally spaced in phase. The circuit uses translinear bipolar second-generation current-controlled conveyors, grounded capacitors and enjoys low active and passive sensitivities and independent current-control of the frequency of oscillation.

A new current-controlled multiphase sinusoidal oscillator using translinear current conveyors

A novel first order all-pass section using a single second generation current conveyor is given. In addition the circuit uses two resistors and only one capacitor. The circuit is also realized with a translinear conveyor. The latter circuit uses only one external resistor and a capacitor. The proposed circuits are verified using PSPICE with attractive results.

Simple first order all-pass section using a single CCII

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.

High frequency applications based on a new current controlled conveyor

A new concept to take advantage of the parasitic resistance that appears on port X of the second-generation current conveyors is introduced. This parasitic resistance, which is controllable in current, leads to the definition of the second generation current controlled conveyors (CCCII). A current controlled bandpass filter, operating in the current mode, is also described. It uses only two CCCII+s and two capacitors. Its central frequency can be adjusted by acting on the bias current of the conveyors. SPICE simulation results, in agreement with theory, are given for central frequencies around 30 MHz.

Current controlled bandpass filter based on translinear conveyors

An equivalent circuit for the translinear implementation of the second generation current conveyors with positive or negative current transfer is given. This circuit takes into account the various parasitic elements of the conveyor which induce frequency limitations (gain values, poles of the transfers, and parasitic impedances). The methods allowing the determination of the values for these parasitic elements are indicated and discussed. The effect of each element on the frequency responses of the circuits using the conveyors are studied in every detail. The frequency behavior of two circuits are analyzed as examples: a voltage amplifier without feedback and two configurations for a second order biquad filter operating in current-mode. All the theoretical results of the analysis are well confirmed from SPICE simulations.

On the frequency limitations of the circuits based on second generation current conveyors

The design of a tunable high-frequency fully integrable current-mode bandpass filter is presented using a complementary high-performance BiCMOS process. The new architecture of this filter is based on impedance simulation and employs current controlled conveyors. The Q-factor and the center frequency can be electronically controlled with dc bias currents over a broad range of values, thus allowing easy tuning of this filter. An application to a mobile communication IF receiver channel centered at 85 MHz and with 1-MHz bandwidth based on the cascade of two identical second-order bandpass cells has been designed. Measurements show very interesting frequency performance (f/sub 0/ tunable in the range 30-120 MHz and Q from 1-140) in conjunction with low power consumption (25 mW for the fourth-order filter with /spl plusmn/2.5 V supplies).

High-frequency high-Q BiCMOS current-mode bandpass filter and mobile communication application

A class AB current-controlled grounded resistor based on a translinear loop implemented from bipolar transistors is described. Simulation results show that its value is tunable from 30 to /spl sim/100 k/spl Omega/ with frequency responses up to 100 MHz and beyond. With 12.5 V supply voltages, the total harmonic distortion (THD) is 2.5 times the value of the control current. To illustrate its suitability, the results of a controlled amplifier, using this resistor and operating in current-mode, are also given.

O. Saaid

Papers

High frequency applications based on a new current controlled conveyor

Current controlled bandpass filter based on translinear conveyors

On the frequency limitations of the circuits based on second generation current conveyors

High-frequency high-Q BiCMOS current-mode bandpass filter and mobile communication application

Class AB current-controlled resistor for high performance current-mode applications