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Monostable Pulse problem 556 timer

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maanas

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I am generating 300us Monostable Pulse through 555 IC with 12V Vcc supply.The frequency is 5Hz. The pulse width is ok but when I see the waveform on the oscilloscope, the pulse shape is not good. The pulse rises to 10V very fast but after that exponentially goes to 11V and while discharging it drops down to 3 V fast but then exponentially discharges to 0V. The Vcc is bypassed with 0.1uF an 1uF capacitors. I am providing negative pulse of 10uS at the trigger input and probing at pin 9.

What can be the problem.
 

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Which exponential time constants do you see? Are you sure the behavior is outside specifications? Also, is your oscilloscope probe correctly compensated?
 

There are no exponential rise and fall when the pulse is slow but as the delay time is increased to above 100uS then this exponential rise is seen on oscilloscope.
 

These distorted pulses, are you seeing them at pins 5 and 9? (output 1 and 2 respectively).
That would be strange, extremely strange on a device with totem-pole output.

Can you take a scope waveform, with the proper vertical scale such that the pulse occupies most of the screen?

Also, do you have any kind of load attached to the output?
 

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