Pulse shortening circuit

Does anyone have any recommendations for a low-power pulse shortening circuit?

i.e. I have an incoming clock pulse and I would like to reduce the duty cycle by a rough amount.

jbeniston said:

Does anyone have any recommendations for a low-power pulse shortening circuit?
i.e. I have an incoming clock pulse and I would like to reduce the duty cycle by a rough amount.

Click to expand...

Depending on the minimum width of the output pulse, you can consider 555 timer, TTL 74121, CMOC 4528,etc ..
:wink:
IanP

IanP said:

Depending on the minimum width of the output pulse, you can consider 555 timer, TTL 74121, CMOC 4528,etc ..
:wink:
IanP

Click to expand...

Thanks. I should have said CMOS circuit.

By putting a capacitor in series, it will create a ramp wave. Send it to a logic gate. The output pulse is shortened.

The percent reduction can be adjusted by use of a potentiometer.

Sample schematic:

BradtheRad said:

The percent reduction can be adjusted by use of a potentiometer.

Sample schematic:

Click to expand...

Hi, i have a doubt...

How can we reduce the amplitude by this potentiometer....

By using this cap we can change the width of the output pulse... am i rite?...

thanks,,,,,,

Do you want it to use in welding machine? Pulse welding type?

If not, I guess you just want to change the width of your signal. If this true, then use micro-controllers to reduce the width. And if you need to change just the amplitude, just use a POT.

Mithun_K_Das said:

If not, I guess you just want to change the width of your signal. If this true, then use micro-controllers to reduce the width. And if you need to change just the amplitude, just use a POT.

Click to expand...

Thanks, but I'm after a CMOS circuit for use in an IC. (I thought that's what this forum was for )

This seems to be something like what I'm after:

http://www.tradeofic.com/Circuit/9900-MONO_PULSE_SHRINKER.html

kenambo said:

Hi, i have a doubt...

How can we reduce the amplitude by this potentiometer....

Click to expand...

Do you mean the voltage amplitude? That is determined by the supply voltage to the logic gate.

By using this cap we can change the width of the output pulse... am i rite?...

thanks,,,,,,

Click to expand...

Yes, if you choose the Farad value (together with the pot value) properly. Together they need to produce a suitable time constant, which will respond within the incoming pulse length.

My schematic shows typical values that will work with 1 kHz.

If your frequency of operation is higher, then reduce the Farad value.
If lower, then increase it.

The potentiometer provides adjustment of the output pulse length. It ranges from zero to about 90 percent of incoming pulse length.

Thanks, and yeah, time constant.. absolutely...

So its a kind of PWM circuit am i right..