>-----Original Message-----
>From: Hulatt, Jon [mailto:jhulatt@MONSTEREUROPE.COM]
>Sent: 22 April 2004 11:57
>To: PICLIST@MITVMA.MIT.EDU
>Subject: [EE:] sine wave generator
>
>
>Hi,
>
>I need to generate a 1300Hz ish sine wave pulse, from a pic,
>that I can plug into a tape recorder's line in jack to log.
>
>Obviously, it's fairly easy to get a 1300 Hz square wave, but
>what can I do to simply and easily smooth this out a bit, so
>it's reasonably close to a sine wave?
>
>Any pointers appreciated
>
>Thanks
>
>Jon


If the signal is always going to be at the same frequency, this isn't too
hard.  You simply need to remove the harmonics to leave the fundamental
frequency using a low pass filter.  You get something approaching a decent
sinusoid, you will need a multi-stage active filter.

Alternatively you could try loosely coupling the square wave to an parallel
LC resonant circuit http://www.wenzel.com/documents/waveform.html

Regards

Mike




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