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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
What is the simplest way to make a 50% duty cycle oscillator with variable frequnency? Are there any "specialised" ICs or do I have to use some kind of flip-flop?
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
4047 should work, or you might try looking for an icl8038 (or one of its clones, like the 2206), which is basically a VCO, along with some circuitry to make sine/triangle waves. Of course it also has an open collector 'sync' output that is a 50% duty cycle square wave. Unfortunately, the frequency tops out a about 1MHz (although things look pretty ugly at that frequency, 100kHz is a more reasonable goal), and are impossible to find for a resonable price. But once you box it up you have a very nice sig gen
Registered Member #528
Joined: Fri Feb 16 2007, 10:32PM
Location: Warsaw, Poland
Posts: 166
jmartis, the scheme I gave in my NE555/GDT thread allows to set on and off times. After stretching horizontally in oscilloscope, it would be easy to set 50% duty cycle.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Tonic wrote ...
jmartis, the scheme I gave in my NE555/GDT thread allows to set on and off times. After stretching horizontally in oscilloscope, it would be easy to set 50% duty cycle.
Maybe, but I think its not easy to set it to exactly 50%, and I doubt it would be stable over wide frequency/load range...
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I think that Wave Rider's idea of having your oscillator running at twice the desired frequency then dividing it by two - is the most reliable way of producing a 50:50 output..
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50/50 duty cycle oscillator
