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From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: A variation on my current mirror low distortion sine wave oscillator - 10dB less distortion and much the same number of components
Date: Sun, 16 Feb 2025 10:14:31 -0500
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"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
> On 16/02/2025 2:18 pm, Edward Rawde wrote:
>> "JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
>>> 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?  You don't need
>>> response at dc.  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.
>>>
>>
>> Is there any specific reason for the npn Q5?
>> Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
>> 2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
>
> Complementary pairs often work better than simple emitter followers.

But it's not a Sziklai pair. Both base-emiiter currents flow through R25

The Sziklai pair has been used for centuries.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf

> John May probably has a good reason for the choice. I've used them from time to time.
>
> https://en.wikipedia.org/wiki/Sziklai_pair
>
> -- 
> Bill Sloman, Sydney
>
>