Shanti Swarup Gupta

Two Simple Analog Multiplier Based Linear VCOs Using a Single Current Feedback Op-Amp

Two simple voltage-controlled-oscillators (VCO) with linear tuning laws employing only a single current feedback operational amplifier (CFOA) in conjunction with two analog multipliers (AM) have been highlighted. The workability of the presented VCOs has been demonstrated by experimental results based upon AD844 type CFOAs and AD534 type AMs.

SYNTHESIS OF LINEAR VCOs: THE STATE-VARIABLE APPROACH

The paper presents a systematic approach of synthesizing sinusoidal linear VCOs (i.e., an oscillator providing linear tuning law of the type f0 ∝ VC between the oscillation frequency f0 and an external control voltage VC). In view of recent interest on current feedback operational amplifier (CFOA)-based oscillators, the proposed methodology has been demonstrated by deriving a class of linear VCOs employing CFOAs and analog multipliers (AM). The workability of the new VCOs has been established by experimental results of the circuits implemented with commercially available AD844 type CFOAs and AD534 type AMs.

Synthesis of New Single CFOA-Based VCOs Incorporating the Voltage Summing Property of Analog Multipliers

Recently, current feedback operational amplifier (CFOA) and analog multiplier-(AM-) based-voltage controlled oscillators (VCOs) have been published in the literature which require 2 CFOAs and 2 AMs for linear tuning law between control voltage and frequency of oscillation. In this paper, a family of eight new voltage-controlled oscillators (VCOs), with linear tuning laws, employing only a single CFOA in conjunction with two analog multipliers (AMs), has been derived through a systematic state-variable methodology. This has been made possible by exploiting the voltage summing property of the multiplier chosen which has never been done in the literature earlier. The workability of the presented VCOs has been verified by experimental results based on AD844 type CFOAs and AD534 type AMs, and the advantages of new circuits over the previously known CFOA-AM-based VCOs have been highlighted.

ELECTRONICALLY-CONTROLLABLE FLOATING INDUCTOR USING OPERATIONAL MIRRORED AMPLIFIER

The operational mirrored amplifiers (OMA) were introduced as useful building blocks for facilitating an easy realization of floating impedances (in conjunction with RC elements) as compared to other approaches of floating impedance simulation. In this paper, we present a new formulation, for realizing a floating inductance (FI) using an OMA which takes into account the dominant pole of the op-amp employed in the OMA and hence, does not require any external capacitor. Moreover, when the only external resistor employed is replaced by an electronically-controlled resistance, the resulting circuit permits an electronically controllable floating inductance. The workability of the proposed FI has been demonstrated by PSPICE simulations.