Peak voltage detector...

[ikelectro]

hi everybody,

Once again I'm here with my questions..... This time I want to build a peak voltage detector for CMOS circuits.....i have googled it first and comes huge nos of circuit.... i chose This one( attached and from http://www.discovercircuits.com) and want to go with this circuit... now the question is : Can I use LM358 replacing the LM393???

thanks in advance!!!!!View attachment peak voltage detector.......pdf

 

[ikelectro]

and can Anyone please explain this circuit for me!!!!!!!!!!

 

[ikelectro]

I have just done with LM358.... here are the result (picture attached) ....... Is it right??? please share your valuable comments on this
input

output

 

[MikeMl]

Without knowing the specs on your DVM and knowing what the input waveform is, there is no way of knowing if your results are correct.

 

[ikelectro]

Without knowing the specs on your DVM and knowing what the input waveform is, there is no way of knowing if your results are correct.

But I dn't have any CRO to find out the wave shape .... but I gave the input from a 555 and i think that is square wave output....
and I use LM358...
Now anything is there for me.. waiting for your reply.....

 

[ronv]

Is it this circuit?
http://www.discovercircuits.com/DJ-Circuits/peakdet1.htm

If so it will work with the 358 except the 358 output doesn't go all the way to 5 volts. That is probably why you measure 4 volts when you should measure 5 volts.

 

[ikelectro]

Is it this circuit?
http://www.discovercircuits.com/DJ-Circuits/peakdet1.htm

If so it will work with the 358 except the 358 output doesn't go all the way to 5 volts. That is probably why you measure 4 volts when you should measure 5 volts.

yes this the same circuit from same source from I linked it here.
so you are suggesting I should use 393???
there is something that i want to asked >> how should I increase the input frequency. because there is only 150KHz range( in the above circuit) ...

 

[ronv]

yes this the same circuit from same source from I linked it here.

Your link only took me to the home page.

so you are suggesting I should use 393???

Yes, if you need it to go to 5 volts and operate at a fairly high frequency. Or use a much faster rail to rail op amp.

there is something that i want to asked >> how should I increase the input frequency. because there is only 150KHz range( in the above circuit) ...

If tou want the frequency higher you need a faster comparator than the 393. It will probably run higher if your signal will always be a square wave like you get from the 555, but if you plan on a sine wave it will need to be faster since the comparator only turns on right at the peak.

 

[ikelectro]

what happen if I chose more voltage at VCC like 9V for LM 358 and say my input signal's source have only 5V, can this solve the problem and always it is square wave. I'll not go for sine wave (i dnt require that)....

If tou want the frequency higher you need a faster comparator than the 393

what will be your suggestion in that case? which IC should I use..

 

[ronv]

Maybe something like this:

https://www.mouser.com/ds/2/405/tlv3202-193866.pdf

 

[audioguru]

The LM358 is an old very slow opamp that has trouble above only 2kHz. The LM393 is a fairly fast comparator that works up to about 150kHz.

Like most cheap multimeters, yours is made to accurate show the level of a 50Hz or 60Hz sinewave from the mains electricity and reads low at higher frequencies.
My expensive Fluke multimeter is accurate to 20kHz and reads low at 150kHz.

 

[ikelectro]

Like most cheap multimeters, yours is made to accurate show the level of a 50Hz or 60Hz sinewave from the mains electricity and reads low at higher frequencies.
My expensive Fluke multimeter is accurate to 20kHz and reads low at 150kHz.

but I dont want to go for the sine wave... want to stick with square wave......
are sure about that mine works perfectly only within 50-60Hz????? but the manual says 20MHz range it has!!!!! ( It is a CIE 8007)....

 

[ikelectro]

The LM358 is an old very slow opamp that has trouble above only 2kHz. The LM393 is a fairly fast comparator that works up to about 150kHz.

Is there any other way to do the thing??? I mean peak voltage detector....

 

[audioguru]

but I dont want to go for the sine wave... want to stick with square wave......
are sure about that mine works perfectly only within 50-60Hz????? but the manual says 20MHz range it has!!!!! ( It is a CIE 8007)....

Your cheap multimeter can measure a frequency as high as 20MHz but measure the level of a SINEWAVE accurately to only 500Hz.

It does not have "true-RMS" so it cannot accurately measure the level of a square-wave.

 

[ikelectro]

It does not have "true-RMS" so it cannot accurately measure the level of a square-wave

Hi Audioguru,
then I think that to get an True RMS meter will be a good idea.... but I think that will be very expensive for me as I am a student who just started walking (2 years!!) into the sea of electronics.......

So can you please suggest me how to get started with peak voltage detector circuit......

 

[audioguru]

You do not have the tools that will measure the peak voltage of a squarewave at a radio frequency.

Your cheap multimeter measures the level of a low frequency sinewave so use a low frequency sinewave.

 

[ikelectro]

are you telling me to go with

1) examine the circuit with sine wave or
2) make a voltage peak detector for sine wave.....

But I need a peak detector for square wave ......

 

[ronv]

What will be your minimum and maximum voltage for your square wave?
What will me the minimum time the square wave will be positive?
What do you want the output voltage to be for the minimum and maximum input voltage?
What are you measureing?

 

[ikelectro]

Hi ronv,

What will be your minimum and maximum voltage for your square wave?

maximum will be 5 volt.......

What will me the minimum time the square wave will be positive?

it depends upon the circuit which one I'll check....

What do you want the output voltage to be for the minimum and maximum input voltage?

cant understand you clearly, may be because I'm not so strong in English !!!!!

What are you measureing?

as project I want to make a peak voltage detector.....

 

[audioguru]

You cannot buy modern high frequency parts and you cannot measure the level of the input signal.
You don't even have an oscilloscope.