REALIZATION OF P, PD, PI AND PID CONTROLLERS USING OTRA

Abstract

Control engineering deals with understanding of plant under operation, and obtaining a desired output response in presence of system constraints. There has been an ever increasing demand of controllers in process industry for improving manufacturing processes and energy efficiency. The evolution of submicron technologies has resulted in the requirement to use low power supply voltages which makes it difficult to design voltage mode circuits with high linearity and wide range. Also as signal processing extends to higher frequencies, the traditional design methods based on voltage operational amps are no longer adequate. However generally analog controllers are designed using operational amplifiers. To overcome these problems circuits operating in current mode, which have the inherent property of higher bandwidth, larger dynamic range and better linearity, are preferred. Various analog building blocks operating in the current mode such as various generations of current conveyor, CDBA, OTA, OTRA etc are available in literature. OTRA being a current mode device inherits all the advantages of current mode techniques, in addition it is free from parasitic input capacitances and resistances. In this thesis OTRA based controllers i.e. P, PD, PI and PID with independent tuning of proportional Kp, derivative Kd and integral Ki constants are presented. These configurations can be made fully integrated by implementing the resistors using matched transistors operating in linear region. To observe the effect of controller on second order system a second order low pass filter is designed and simulated. In order to verify the functionality of proposed controller circuits, a closed loop control system using the proposed controllers and second order LPF is designed and simulated using SPICE.