Study of multistage digital oscilloscope trigger circuit

Abstract

This paper describes a general equation of the input and output relation in N-stage configuration of a trigger circuit, which outputs a sine wave (or a cosine wave) with a zero phase at the timing when a trigger signal input is applied. Its conventional configuration employs two or three stages of a track hold circuit and an analog multiplier with some glue circuits, and it is targeted for a digital oscilloscope. Our N-stage trigger circuit can average non-ideal characteristics of each phase with N stages, and it is expected that a high precision trigger circuit can be realized. This may lead to analog circuit realization with low supply voltage; in other words, each analog circuit is not precise but the whole trigger circuit is precise. Also, its application as a pre-stage of the successive approximation time-to-digital converter for one-shot timing measurement is proposed.