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Design >> Analog Design >> pure sine wave generator
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Message started by analog2000 on Jul 22^nd, 2007, 7:36am

Title: pure sine wave generator
Post by analog2000 on Jul 22^nd, 2007, 7:36am

Hello,
I have to design a blockthat can generate spectrally pure sine waves voltages around 10KHz. I am contemplating using a high Q bandpass filter to convert a square wave into a sine wave, would anyone like to share their thoughts about this problem ?
thanks a lot
Best Regards
analog2000

Title: Re: pure sine wave generator
Post by jp314159 on Aug 2^nd, 2007, 1:07pm

Generate a clock signal at (say) 16x the 10kHz, and use a DAC to stairstep approximate the sine. At 16x, you will only have harmonics present that are > 160kHz, and so very easy to filter.

At 16x, in fact, you only need 4 or 5 DAC values, assuming you do the 180°-360° portion by inverting the first half. You can build the DAC with just a string of a few resistors and tapping off (taps at sin(15°), sin(30), sin(45) etc.). Send the output of the DAC simultaneously through 2 opamps -- one a follower, and the other a gain of -1. Using logic, alternativerly select the +1 and the -1 path.