How to generate 30kHz sine wave?

Hi Nic,

an established way to produce a sine wave is to use the UAF42 state-variablle filter. Make a search in this forum.

I prefer using the Wien bridge in the feedback loop of an OPAmp with JFET amplitude stabilization.

Another methode is to produce a square wave and to filter out the harmonics.

And and and...

Kai

The available power supply will be 3.3V or 1.8V. Max size better to be smaller than 5mm*5mm.

Hi Nick,

A TLC555 or NE555 timer could be set up in astable mode as a 30 kHz square wave oscillator. You would have to use the common astable circuit that includes the silicon diode in the RC circuit, in order to achieve a 50 % duty cycle. The timer would be followed by an active low-pass filter.

It is difficult to know just how extensive an active low-pass filter would be needed to result in a sine wave having less than 1 % harmonic distortion. An ideal square wave is made up of only odd harmonics, but chances are the square wave won't be perfect and some level of even harmonics will be present in the waveform.

I suggest trying a two-stage, forth-order low-pass active filter after the TLC555. You should be able to use TI's new Filter Design software (beta version) to synthesize the filter. The filter output waveform may look quite sine-like when viewed with a DSO, but a distortion analyzer would be needed to determine the actual per cent distortion.

Regards, Thomas

Precision Amplifiers Applications Engineering