Re: A variation on my current mirror low distortion sine wave oscillator - 10dB less distortion and much the same number of components

On 15/02/2025 6:41 am, JM wrote:

On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

Basically same idea, but two separate controllable asymmetric current
mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
>
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components.

 What is the point of a push-pull current mirror?

It starts up faster.

You don't need response at dc.

But you do have to wait a while for blocking capacitors to charge up.

 A "class A" (for want of a better term) mirror with
minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.

About 140dB down, compared with the 80dB I got, even after I'd pushed up the damping resistor at R6 from your 47k to 220k. Even then, I cut 5 seconds of simulation time before I was game to start the FFT.
--
Bill Sloman, Sydney