Modified Astable Multivibrator

209

03:09:55

A modified version of the classic astable multivibrator, to provide a higher-driven output with cleaner square wave oscillations.

published 8 years ago

VVPCEMPEROR

8 years ago

That's pretty cool I couldn't make something like that

BillyT

8 years ago

Putting a current trace on the led and the power supply shows that a bit more work may be necessary.

Issacsutt

8 years ago

Thanks!!!

Issacsutt

8 years ago

Yeah I've considered improvements can be made, my main goal was to provide a more stable output that can have a 50% duty cycle unlike the 555 timer (to drive flip flops), and still use common components.

BillyT

8 years ago

The 555 can have a 50 % duty cycle, just make R1 10% R2. (Say 1k & 10k) adjust the capacitor value for frequency.

Issacsutt

8 years ago

But every source I've read has said you need to add a diode to get an equal rise and fall time for the 555.

selman

8 years ago

No actually you don't necessarily need diodes there is a 555 topologies that provide 50% duty cycle with even less components than the standard astable multivibrator.

selman

8 years ago

http://everycircuit.com/circuit/5989063141359616

Issacsutt

8 years ago

Ok cool! Didn't know you could do it like that, what's the formula for the period?

selman

8 years ago

The rise time is Tr = ln(2)RC, assuming equal rise and fall time the period will be T = ln(4)RC.

hurz

8 years ago

This 50% is only possible for the CMOS rail2rail version of 555 possible. The BJT version does drop the high level by upto 1.5V below Vcc.

Issacsutt

8 years ago

That makes more sense, thank you hurz.

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