Method of op-amp speeding increase, basing on introduction of the nonlinear differentiating circuit

Abstract

The method of the high speed increase and the transients for the large signal in operational amplifier (Op-Amp) is considered. Base structure of Op-Amp, which is classical, contains the basic correcting condenser, providing stability of Op-Amp, the compensating capacity driver (DCc∗) and the buffer amplifier. For increase on 1–3 order of the slew rate (SR) of the output voltage increase in such Op-Amp the nonlinear differentiating circuit is introduced. This circuit is realized on the basis of the additional differential stage (DS2) and differentiating capacity. Thus DS2 practically don't influence on some static and small-signal dynamic parameters of Op-Amp, but on the large signal in during leading edge of the input signal, when basic differential stage of Op-Amp enters into a nonlinear mode, he differentiates input voltage and forms the large recharge current of the basic correction capacity. As consequence, SR of Op-Amp essentially raises. Feature of Op-Amp of the given class is the opportunity of the differential stage to work in the micocurrents mode. The decision of the nonlinear differential equation describing transients in Op-Amp is received. This decision allows designing the concrete circuit-technical decisions of Op-Amp within the framework of modern microelectronic technologies, including BJT, SiGe, CMOS, BiJFet, etc. The results of computer simulation confirming of the efficiency of the suggested circuit-technical decisions are given. So, in the micro-powerful BiJFet operational amplifier admitting the work at low temperatures and influence of a penetrating radiation, maximal SR of the output voltage increase increases up to 3000–4000 V/μs.