Transients in the operational amplifier with a square-law transfer characteristic of the compensating capacitor driver

Abstract

The non-linear operating mode of the differential operational amplifier (Op-Amp) with a 100% negative feedback is considered for the case where the open-loop Op-Amp is represented by the first-order transfer function, and the non-inertia driver of the basic compensating capacitor of the Op-Amp has a square-law transfer characteristic. The versions of construction of such drivers and Op-Amp are shown on the base of radiation-hardened array chips ABMK-1.3÷2.1, which enable to operate at low temperatures. During the front of the transient these circuit solutions of the Op-Amps provide large currents of the correction capacitance recharge (units-tens of milliamperes) at low power consumption in the static mode and allow for significant increasing of the maximum slew rate (SR). The nonlinear differential equation is obtained that describes both the transient in the Op-Amp and the steady-state mode. Its solution enables to realize the parametric synthesis of practical schemes of the high-speed Op-Amp. The computer simulation results of the correction capacitance driver with the square-law transfer characteristic and the corresponding operational amplifier are presented. They show that the terminal parameters for the SR are limited by the permissible amplitude of the transient overshoot in the Op-Amp and essentially depend on the order of the transfer function of the open-loop Op-Amp on the frequencies exceeding the unity gain frequency.