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rajchakraborty
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Join Date: May 2010
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square wave generator

05/27/2010 7:15 PM

for designing a square wave generator, which type of multivibrator or any other ckt will be most helpful?

if I design through multivibrator,Iwant to know,wheather I should use IC 555 or not,for better output?
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JohnDG
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#1

Re: square wave generator

05/27/2010 7:42 PM

Start with your requirements - "better output" is pretty meaningless. What do you actually need?

  • Wide frequency range?
  • - How wide?
  • - What range?
  • High stability?
  • - What's your target ppm/°C?
  • Is a symmetrical output important?
  • What rise and fall times do you need?
  • and so on.

Work out what you want from your circuit, then you can work on how to achieve it.

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redfred
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#3
In reply to #1

Re: square wave generator

05/27/2010 10:07 PM

GA

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Tobugrynbak
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#2

Re: square wave generator

05/27/2010 9:12 PM

You can do it by using 2 elements of a 74HC14 (or any hex invertor) set up the first one as an oscillator and the second as a buffer. The output of the second will be a square wave of near rail voltage (4.5V) proportion @ 5V VCC.

Refer to the Philips data sheet AN-456 and the Fairchild data sheet AN-140

Easy peasy, rock solid reliable minimal component count.

Oh and use NPO capacitors in your oscillator that will improve frequency stability.

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redfred
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#4
In reply to #2

Re: square wave generator

05/27/2010 10:18 PM

I don't know, what if the output voltage swing is supposed to swing between 0 and 24V for the input to a PLC. TTL chips are a very common family of circuitry, and thus will work in many places. They don't work everywhere.

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Tobugrynbak
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#5
In reply to #4

Re: square wave generator

05/27/2010 11:42 PM

The fact that he mention a 555 timer, sort of indicated that he was operating at TTL voltages.

If he is looking for a larger voltage output swing then he could tack on an op amp like say LM321 and run the op amp off a +/- 15-20 volt rail.

There are plenty of published circuits around for the OP to peruse.

Unfortunately there was a dearth of information by the OP as to what was the desired parameters beyond a square wave generator. Which as you know makes it difficult to provide informed suggestions.

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garth
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#6

Re: square wave generator

05/29/2010 12:35 AM

Whilst the OP has not given much info, I suggest the 555 timer for which there is an enormous amount of information on the internet. If two of these are used in conjunction variable pulse width and frequency can be obtained, also the 555 output can easily drive a power mosfet for higher power and voltage output. Frequencies of 200KHz should be possible.

However without further info this is just a starter suggestion.

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rajchakraborty
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#7
In reply to #6

Re: square wave generator

05/30/2010 4:42 PM

thanx a lot.

I am just going to design it.

the other specifications are yet to get, depending on project requirement.
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