On the selectivity of a resistance capacitance network

Abstract

A resistance, capacitance network, used in circuits for generation (Wien bridge oscillator) and measurement (Wien bridge) of low frequencies, has been analysed for the maximum selectivity condition by defining a design parameter n. It has been shown that a lower value of n gives (i) a more selective response and as such, a purer waveform in the oscillator circuit and a sharper null point in the Wien bridge circuit and (ii) a more favourable condition of operation of the active device in the oscillator circuit. The effect of cascading such networks on the selectivity of the resultant transfer characteristic has been discussed.The effect of interchanging the series and the shunt arms of the network has been considered. It has been shown that if n is high, the resulting network has a characteristic similar to that of a Wien bridge and is superior to the latter in some respects.