Prediction of Propagation Delay in RTL Circuits by Charge Control Approach

Abstract

ABSTRACTThis paper describes a charge control approach to the analysis of the transient response of an RTL inverter. The procedure adopted in predicting the propagation delay of RTL inverters consists of a preliminary worst case d.c. design of the circuit, followed by the evaluation of the individual components of the propagation delay time, viz. the storage, fall, delay and rise times. In the calculation of switching times, the driving waveform which is actually an exponential time function is approximated by a ramp time function.The present investigation has yielded formulae which enable the prediction of propagation delay time as a function of the fan-in and fan-out and the value of the transfer resistance. This analysis enables the circuit designer to choose such values of the circuit resistances which will yield minimum propagation delay under the worst transient conditions without violating the d.c. stability criteria. Experimental verification of the predicted times has also been carried out.