hi..........
i have problem to change the duty cycle....
i have i/p of 9 volts square wave of 50% duty cycle....
but i want to change that 50% to 20%-10% duty cycle......
anybody plz help me out....how can i achieve???
thank you
rky

 

Lots of different ways, here's one.

 

but can i get 3Mhz frequency from this circuit of 20% duty cycle.....????
is 555 works on 3Mhz???

 

What other criteria can you tell us that were not in your original question?

Do you have a circuit that is producing the square wave? Can that circuit be modified? Do you need a variable duty cycle, or just anything in the range of 10 to 20%? Etc.

John

 

A TLC555 (a CMOS 555 from TI) goes to 2Mhz, I'm not aware of any other 555 chips that go higher. You have one in mind?

hi..........
i have problem to change the duty cycle....
i have i/p of 9 volts square wave of 50% duty cycle....
but i want to change that 50% to 20%-10% duty cycle......
anybody plz help me out....how can i achieve???
thank you
rky

You didn't mention 3Mhz on the first post. Little details like that are important.

 

thanks for your response..
oh i m sorry.........yes i have 3Mhz frequency of 50% duty cycle.....
so can i make it of 10%-20%.....?????
its not require to have accurate duty cycle of 10% or 20%.....
but roughly it will ok....nd it is not necessary to vary duty cycle...
i want to just keep my frequency at lower on time and higher off time....thats it...

and @john i generated 3Mhz from 4016 nand gate ic.....nd that wont be changed......
thank you

 

and @john i generated 3Mhz from 4016 nand gate ic.....nd that wont be changed......
thank you

Why? You can often adjust the duty cycle of Inverter/NAND-based oscillators quite easily.

John

 

@ john can i change duty cycle from inverters???
that i dont know...
how???

 

@ john can i change duty cycle from inverters???
that i dont know...
how???

Yes, by controlling the charge/discharge times in an analogous way to what Bill suggested for a 555. Here is just one of several ways to do that:

If you would post your circuit, we might be able to give more definite advice.

John

 

yes sir i did this......but i got at o/p side variable frequency not variable duty cycle....
i put constant capacitor and potentiometer.....
so what should i do further???
have i to change capacitor value for variable duty cycle??
thank you

 

Please provide your schematic.

Suggested reference: http://www.fairchildsemi.com/an/AN/AN-118.pdf

John

 

the same schematic you posted, i have....
there is capacitor value of 10pf and used potentiometer..and nand gate ic 4093
and you gave me the link but i coudnt find that how to change duty cycle...
thank you

 

We seem to be having a communication problem. Your initial question referred to a fixed frequency and duty cycle oscillator based on a NAND gate. The schematic I posted is not that.

The link I gave does not describe how to adjust duty cycle. It does describe how the oscillator works. That information, comments in this thread by myself and others, and the rough schematic I provided should enable you to see how to adjust the duty cycle.

Without knowing exactly what your design is, I simply cannot give more advice. I will add that the schematic I posted did provide variable duty cycle down to the limits you want.

John