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# How to make a pure two sided sine wave generator with astable multivibrator?

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#### sr13579

##### Member
Hello again,
I wanted to make an oscillator that provodes a sine wave. I don't have an oscilloscope with me but I simulated this and found that the sine wave is always at positive side. I want to make sonething that can give me half positive side and half negative side sine wave using one sided square wave. Can you show me a circuit please?

There are many circuits that produce a sine wave. Please show your schematic.

1) sine wave is always at positive side.
2) half positive side.
3) half negative side.
4) one sided square wave.

If you square wave was unipolar (0V to some +V) and you filtered it to produce a sine-wave, then your sine-wave will also be 0V to some +V.

Assuming this, use an series capacitor to DC-block your output sine-wave or the source square-wave and that should fix the issue.

There words you are looking for are:
Two-sided => bipolar (-V to +V)
One-sided => unipolar (0V to +V)

There are many circuits that produce a sine wave. Please show your schematic.

1) sine wave is always at positive side.
2) half positive side.
3) half negative side.
4) one sided square wave.
Output sine wave is Half negative side and half positive side(2 and 3 both). I have added the circuit I was working on.

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If you square wave was unipolar (0V to some +V) and you filtered it to produce a sine-wave, then your sine-wave will also be 0V to some +V.

Assuming this, use an series capacitor to DC-block your output sine-wave or the source square-wave and that should fix the issue.

There words you are looking for are:
Two-sided => bipolar (-V to +V)
One-sided => unipolar (0V to +V)
I want the bipolar one.(Thanks for the information I am totally new at this)

Yeah, stick a largeish capactiro in series with the output. If it's a polarized capacitor, mind the polarity.

A capacitor blocks DC but passes AC. That is what you want, a coupling capacitor. Its value is simply calculated for the lowest frequency to pass without much loss.

Yeah, stick a largeish capactiro in series with the output. If it's a polarized capacitor, mind the polarity.
You also need a resistor to ground at the capacitor output.
10kΩ is a typical value.

Output sine wave is Half negative side and half positive side(2 and 3 both). I have added the circuit I was working on.
So that's what, a square-wave generator with a third-order low pass filter? Is that right? Not sure the quality of the sine wave you'll get out of this.

Some sinewave oscillators use a squarewave filtered by an 8th-order switched capacitor lowpass filter IC. I made a stepped sinewave from a CD4018 with a few resistors and filtered it with two 4th-order switched capacitor lowpass filter ICs and the distortion was so low I could not measure it.

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