The Non-Linear Differentiating Circuits of Correction of Transient Process in Differential Operational Amplifiers

Abstract

The nonlinear equivalent circuits for small and large signals of the input circuits of the classical BJT operational amplifier (Op-Amp), which relates to the basic functional nodes of analog-digital interfaces of modern automatic control systems and it has a significant effect on some of their dynamic parameters, are discussed. This enabled us to formulate a circuit method for connecting a differentiating correction circuit (DCC) of the transient to the standard Op-Amp. Such solution reduces significantly the recharging time of the Op-Amp integrating capacitor (C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c1</inf> ), which forms the given phase margin and the unity gain frequency. It is shown that, on a small signal, the additional differentiating capacitor C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c2</inf> has practically no effect on the Op-Amp operation; however, it increases the maximum slew rate (SR) at the dynamic overload of the main Op-Amp input stage. The estimates of the SR limiting values are given with regard to the lag effect of the main Op-Amp functional nodes. The proposed method of connecting a differentiating correction circuit effectively works both in the Op-Amps and in other electronic devices of automation and robotics (continuous voltage stabilizers with differential stages, comparators, etc., implemented by modern technological processes - BJT, BiJFet, SiGe, CMOS, SOI, SOS, etc.).