[3rd round] AN67 Ultra-low THD 10kHz sine oscillator PCB Group buy.

[klewis]

That result is from my HP8903a. It's the best the 8903 can do, not the oscillator. To get the actual distortion, I would need to calculate it from the measured harmonics, of which only the 2nd is visible. Even the 2nd might be an artifact from the active twin-t filter I used to null the fundamental.

I just hand calculated the THD using the -126 db for the second and -134db for all others - as the actual harmonics are lost in the noise floor of -134. I get 0.00007% THD. An Hp3562 was used for the fft. As I mentioned Dick Moore's active twin T was used to null the fundamental by approx. 50db to get the harmonics to show within the range of the 3562 (range approx. 80 to 85 db). I also have a KH4402, the noise floor on the AN67 looks to be about 8 to 10 db lower than the KH4402.

Ken

 

[cobretti]

I agree.... for a few pp-billion, it must be a lot better. What thd numbers did you get and what did you use to measure it?

Thx-RNMarsh