lm567

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ariakovo

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I want to detect if there is a 40KHz frequerncy.So I create a 40KHz frequency with a NE555 and then I put the output of 555 in the input of the 567.The out of the 555 is 5 Volt peak to peak +2.5 offset.I use a ceramic capacitor in the input of 567 (100nF).I use the two formulas to find the capacitors and the resistors and the circuit doesn't works.The output doesn't goes up when i put the frequecy.I have to say that i use a ceramic capacitor for the bandwidth of the filter in the 2 pin of 567.Can someone suggest values for ceramic capacitors and resistors for 40KHz because it doesn't works.Thanks in advance.

https://www.electro-tech-online.com/custompdfs/2008/03/LM567.pdf
 

It should work.
Can you post your exact schemetic, Or email it to me.
Include all your part values on it!

Gary
 
Acommon error people make with the 567 is not putting a pull-up resistor on pin 8(output). It is a open collector output.
 
chemelec said:
It should work.
Can you post your exact schemetic, Or email it to me.
Include all your part values on it!
Gary
Click to expand...

Hi i think that i find the problem.See the schem.I use in the place of R1 = 250hm: C1=100nF.I didn't put input signal capacitor and C3 and the whole thing worked.Also i put and a capacitor between GND and 8 pin because i see in the oscillocope a frequency 40KHz with on time 99% and of time 1%.After a BJT and it worked.I don't know why when i remove the C3 the circuit goes on.But it worked.Thanks anyway

 
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