Multivibrator circuit having compensated delay time

Abstract

A multivibrator circuit used as a delay element. A pair of complementary signals to be delayed control the transistors of a long tailed pair so as to generate charging and discharging currents for a capacitance coupled between first and second current branches of the multivibrator circuit. The delay time depends, among other parameters, on the exact values of these currents. In order to avoid the necessity of providing very accurate values of the signals for generating the proper current values, a current division is applied, to the circuit by adding in parallel to each long tailed pair transistor, a constant current source. As a result the currents in the multivibrator circuit can be switched between two exactly determined current values by alternately switching the long tailed pair transistors fully on and off. The same kind of current division is applied to the circuit in order to achieve a voltage swing at the output which is independent of the current adjustment.