555 Multivibrator Circuit

Published:2011/7/8 9:49:00 Author:Robert | Keyword: Multivibrator | From:SeekIC

By using the 555 time-base circuit it can make up many kinds of self-excited multivibrator and its basic circuit is shown in picture a. When the circuit is firstly connected to the power, the C has not been charging in time, the 555 circuit's pin 2 is at low voltage level. This makes its pin 3 output high voltage level. When the C is in the status of Vc≥Vcc, which is charged by the power through RA and RB, the pin 3 output port would be changed from high voltage level to low voltage level. And the capacitor C would discharge through the RB and internal circuit's discharging switch tube. When it is discharged to Vc≤Vcc, the output port would be changed from low voltage level to high voltage level again. At this time the capacitor would be charging again. This process would cycle to proceed and it would form the self-excited oscillation. The picture (b) shows the waveform of voltage on the output port and capacitor C.



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