Square Wave needed

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#22
I built the Sine-to-Square circuit that jgedde drew/posted above.

Works well too. Possibly better in that it has "flatter" tops. The "comparator" version had a touch of a slope (but may do better if I tweaked some component values).

I have not measured output current drive, or bandwidth yet...gotta work tomorrow.zzzzzz
No need to show waveforms...imagine nice squares.
(both were unaffected by my fluorescent work lamp.)

DSCN3558-1.jpg





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#25
jgedde said:
Try this... It uses what you have in stock. Don't forget power and ground on the 4013 (not shown).


Cheers,
John
Click to expand...


Replacing the 4013 with the 74HC393, does this look right?
(grounding the unused CLK and the two Master Reset pins ?)

393_delete.gif



(this stuff is re-peaking my interest to finish my modular synth that's been collecting dust.)

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#28
Take a look at the 74HC4046 (or similar variants) phase-locked loop chips. They make a very nice, very square, 50% duty cycle, frequency adjustable stand-alone square wave generator at trivial cost (under a buck) and very little effort.

Ignore all the "phase comparators" and just use the Voltage Controlled Oscillator (VCO) portion of the chip. Selecting a few resistors (make R2 a pot to make it variable over a huge range) and a capacitor is about all you need. Couldn't get much simpler, and you can even control the frequency by a DC voltage if you want. Only weak point is not the best jitter so don't use it to clock your DAC.

If you use the 74HC, -HCT, or -LV types you'll be limited to ~5V P-P (though you can go to tens of MHz, should you want). If you don't want to fool with power supplies and need under a few 100kHz, get a CD4046 (or other metal gate version) and power it from a 9V battery (it can run from up to 15V).

Just go to digikey, and search under "4046". You can download the data sheet there, too.
 
#31
EDIT....does not work well. Maybe 100mA is not enough (5v).
Should have checked it better before posting.

Will not produce a square at under 1k @1v sine input....must increase to 2v input to get a square under 1k Hz
Tops slanted.
Almost threw it over my backyard fence.
I think the 393 does not work well at lower freqs ??
I might abandon that chip.
The 4013 seems to work better.
I could go in there and alter it for the 4013.

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#34
Sounds right... The 4013 can source more current than the HC393. You could buffer it with a C240 or a C244...

I figured you use this to drive an amp with a typical 47k input Z where it wouldn't need to source large currents...

John
 
#35
jgedde said:
Sounds right... The 4013 can source more current than the HC393. You could buffer it with a C240 or a C244...

I figured you use this to drive an amp with a typical 47k input Z where it wouldn't need to source large currents...

John
Click to expand...

Changed to the 4013. ....Bette now.
I appreciate everyone's help.

I realized I had an HP 8010a pulse generator (has square wave ) in storage... but
it's size is.... :wchair:



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