Electronically Tunable Dual-Input Integrator Employing a Single CDBA and a Multiplier: Voltage Controlled Quadrature Oscillator Design

R Nandi,Sagarika Das,Mousiki Kar

doi:10.1155/2009/835789

Abstract

A new dual-input differential input active integrator using a current differencing buffered amplifier (CDBA) is proposed. A multiplier element is appropriately used in the circuit whose control voltage (Vc) tunes the integrator time constant (τ) electronically. The design of a voltage controlled quadrature oscillator (VCQO) based on the proposed integrator had been satisfactorily implemented. A new type of measurement for the tuning error of the oscillator based on the Nyquist plot is presented that shows an error of only 2% atfo≈1 MHz with Total Harmonic Distortion (THD) less than 3%.

Highlights

With the advent of the current differencing buffered amplifier (CDBA) building block [1, 2], various analog signal processing/conditioning circuit realisation schemes using this element appeared in the recent literature [2,3,4,5,6]
The CDBA offers several advantageous features viz., high slew rate, improved bandwidth, and accurate port tracking characteristics when configured with a pair of matched current feedback amplifier (AD-844-CFA) devices [3, 4] which leads to extremely low active circuit sensitivity
We propose here a new electronically tunable differential integrator using a CDBA; the control voltage (Vc) of a multiplier element, incorporated suitably in the circuit, tunes τ electronically

Summary

Introduction

With the advent of the CDBA building block [1, 2], various analog signal processing/conditioning circuit realisation schemes using this element appeared in the recent literature [2,3,4,5,6]. We propose here a new electronically tunable differential integrator using a CDBA; the control voltage (Vc) of a multiplier element, incorporated suitably in the circuit, tunes τ electronically. The ICL-8013 device is a four-quadrant analog multiplier whose output is proportional to the electronic product of two input voltage signals with a transmission constant kvolt−1 [7, 8]. The high accuracy (±1%), relatively wide bandwidth (B = 1 MHz), and improved versatility make it quite suitable for analog signal conditioning and active filter design applications. Albeit various CDBA-based active filters/oscillators [3,4,5,6] are available, the feature of electronic tuning in the CDBA active function circuit had not yet been reported. The proposed functions had been verified by PSPICE macromodel simulation of the AD-844 based CDBA and by hardware circuit tests

Analysis

VCQO Design

Simulation and Experimental Results

Findings

Conclusion