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?
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.
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.