555 timer with 50% duty cycle question

Hi, does anyone know how I could get a 555 timer to operate in astable mode at a 50% duty cycle? All the circuits I've seen are always for greater than 50%. thanks.

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It's easy with the CMOS version of the 555 timer...

Tie Threshold and Trigger together, capacitor to ground from this node, likewise a resistor to output... voila, 50%.

...Jim Thompson

|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Jim Thompson

On 27/12/2006 the venerable panfilero etched in runes:

Yes. Go here:

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and download the data sheet. Look at page 10 (figure 14). IT shows you exactly how to do it.


John B
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John B

You go to sci.electronics.basics where this sort of question belongs, and you look for the answers to your post asking the very same thing there.


Reply to
Michael Black

While there are ways to get close with feedback, one can get closer with a flip/flop set to toggle. With two flip/flops, you can get four phases of quadrature output. The '555 has to run at 2 or 4 times the desired output frequency, though.

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