Pulse width modulation control of signal generator - has saw tooth generator output processed through threshold stage to generate gating signal for trigger output stages

摘要

A signal generator produces a square wave output that has a mark-space ratio that is proportional to an input voltage. The circuit is designed to avoid changes in mark-space ratio due to temp. variations and changes in the saw tooth generator that forms the basis of the circuit. The saw tooth generator (1) output is processed over a threshold detector (4) that generates a constant voltage amplitude output that is inverted (5) and used to gate two trigger stages (2, 3). The input voltage (Ve) is gated into the trigger stages by the saw tooth generator. With the input voltage (Ve) equal to zero both output waves (V1, V2) have mark-space ratios of 1:1. The ratio changes when the input changes. The threshold stage ensures that the ratio remains constant even though the saw tooth generator output amplitude may change.