How can i convert square wave to sine wave

[holax12]

I need to convert a square wave to a pure sine wave, how can this be archeived in its simplest form. Thanks

 

[ericgibbs]

I need to convert a square wave to a pure sine wave, how can this be archeived in its simplest form. Thanks

hi,
What frequency.?

 

[grim]

can you define 'pure'?

what sort of power level as well? there are waveform generators that are good at sine waves, but not if you need 15kw

 

[holax12]

Actually i want to convert the square wave generated from an astable multivibrator to sine wave and use it as a rf generator. The frequency is 100mhz.

 

[BrownOut]

Do you have an astable multibrator running @100 MHZ??? I have a multi running a few 10's of KHZ, and I generate a sine wave from it, but I can't even think about running at that freq.

EDIT: for that freq, just use an RF oscillator, and generate the sine wave directly.

 

[holax12]

The rf generator i know is LC tank circuit and it is not stable, slight torch on any part usually alter the frequency. So i want to use astable multivibrator to generate stable frequency.

 

[BrownOut]

Use an rf generator, and don't touch any of the parts. You aren't going to get an astable multi to run at your frequency.

 

[holax12]

Thanks for ur reply @ Brownout.

What if i get the astable multi to work at the frequency i want will it work as an rf generator.

 

[mneary]

Keep torches away from your LC.

 

[Nigel Goodwin]

Thanks for ur reply @ Brownout.

What if i get the astable multi to work at the frequency i want will it work as an rf generator.

You won't, so it's a pointless question.

 

[stevez]

Theoretically (and practically to some extent) if you have a low frequency square wave then you have higher frequency components though at profoundly lower power levels than the fundamental frequency. A filter might help push down the stuff you don't want - leaving the part that you do want. This seems clumsy but it might serve your purpose.

I know in amateur/shortwave radio they used to have a crystal "calibrator) that delivered RF at various specific intervals all over the RF spectrum. I recall seeing some solid-state circuits that I'd guess were square wave generators rich in RF. One would adjust the marker against a known standard like WWV.

 

[Hero999]

Using SMT components it's possible to build an astable multivibrator that'll run at 100MHz.

It's a silly idea though, you're better off using an LC oscillator.

 

[marcbarker]

Is this an FM transmitter? In high power output stage of a transmitter a MOSFET in class c is practically making a square wave, often the gate driven by logic IC or MOSFET driver. The LC 'Pi filter' which matches the antenna turns it into a sine wave.