Low THD sinewave generator

[david77]

Hi guys.

I'm in the first stages of a new project and the need for a low distortion sinewave generator has arisen.
So I'm looking at circuits and I'm not quite sure what to use.

What I want:
-------------------
- THD <1%
- Frequency: Switchable 333Hz, 1kHz, 3.15kHz, 6.3kHz, 10kHz, 15kHz, 20kHz
- Output voltage 1,55Vrms

So what would you suggest? A Wien-bridge? Using an XR2206?

David

[jimmc]

XR2206 will struggle to meet 1% distortion, Wien bridge based oscillators can easily achieve it.
http://cds.linear.com/docs/Application%20Note/an43f.pdf p 29
or if you want to go to extremes
http://cds.linear.com/docs/Application%20Note/AN132f.pdf

However if you want frequency stability better than around 1% look at DDS
http://www.analog.com/library/analogDialogue/archives/38-08/dds.pdf

Jim

[T4P]

Go for wien bridges for low THD and not too high frequencies...(I'm thinking high = >20MHz)

[david77]

I thought I might go the Vienna way .

Thanks for the literature, Jim Williams has been busy. Something to read in bed tonight.
I'm purely in the audio spectrum, nowhere near 20MHz, if I can achieve <1% THD and maybe 5% frequency and amplitude accuracy I'll be happy.

[T4P]

I thought I might go the Vienna way .

Thanks for the literature, Jim Williams has been busy. Something to read in bed tonight.
I'm purely in the audio spectrum, nowhere near 20MHz, if I can achieve <1% THD and maybe 5% frequency and amplitude accuracy I'll be happy.

Then that will make you a nice audio gen. Good luck!

[tekfan]

I know I've posted this lonk in another thread but I am so impressed with this oscillator that I have to post it again:
http://sound.westhost.com/project22.htm

It's THD was below 0.02% when I measured it on a Hameg distortion analyzer. It wasn't even meant to measure such low distortion, so it is probably even lower than that.

This is a great little oscillator for audio work and measurments.

[david77]

Stupid me. Why didn't I look at Mr. Elliot's truly magnificent site? That's basically exactly what I had in mind, push-pull output and all.

Thanks tekfan.