Synthesis of high-speed devices using integrated operational amplifiers

Integrated operational amplifiers include corrective networks preventing self-excitation but also reducing the speed. It is necessary to ensure the minimum speed reduction for the networks. This imposes stringent constraints on the transient response characteristics such as maximum permissible rise time and overshoot amplitude, and on the corner frequency and the nonuniformity of the amplitude or phase-frequency characteristic. These requirements are examined quantitatively by the method of transfer functions in feedback systems. In the synthesis of such a device, one must strive for a characteristic equation with real roots for the transfer function of the feedback loop and one with the largest possible imaginary parts of the complex roots for the amplifier again. For complete matching of design with performance requirements, the corrective network must have as many loops and degrees of freedom as there are equations, A corrective network which has no zeros and does not raise the degree of the characteristic equation is designed for operation of this amplifier under a large capacitive load. With stray shunting capacitances at the output and with slow power transistors, this operational amplifier must be described by a transfer function with three poles. Numerical values of the various parameters are obtained on this basis.