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555 Monostable Circuit with a Changeable Width

2015-02-04 10:09  
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555 Monostable Circuit with a Changeable Width
For a general monostable circuit, the pulse width output is a fixed value. As shown in the picture 2-9, pulse in the circuit uses a closed loop to control the manipulative terminal after being magnified, when trigger frequency rises, the temporarily stable pulse width will be narrowed, thus the duty cycle of the wave output remains unchanged. C2 and R2 trigger the signal input differentially. As the trigger frequency increases, the direct level increases, Vc terminal decreases, and output width of 555 is narrowed. Loop-controlling makes duty cycle output remain unchanged. Suitable frequency scope for the parameter is 500~5000Hz.When design the circuit, this condition should be guaranteed:R1C1≤1.1Tmin=1.1/fmax,fmax refers to the maximum frequency of trigger signal input.