Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Bill Sloman <bill.sloman@ieee.org>
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: Wed, 12 Feb 2025 15:15:57 +1100
Organization: A noiseless patient Spider
Lines: 874
Message-ID: <voh7a5$26aqj$1@dont-email.me>
References: <voc5mp$138ut$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Wed, 12 Feb 2025 05:16:07 +0100 (CET)
Injection-Info: dont-email.me; posting-host="fa5fd19412cd90804b70d9cbbe529824";
	logging-data="2304851"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/dTekEf/hMiZYARMrsh7aQmoxcyVHg9ZI="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:W5uBj4BmJjZ0NuZIx4tF8kgw4kQ=
Content-Language: en-US
X-Antivirus-Status: Clean
X-Antivirus: Norton (VPS 250211-10, 12/2/2025), Outbound message
In-Reply-To: <voc5mp$138ut$1@dont-email.me>

On 10/02/2025 5:18 pm, Bill Sloman 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.

Splitting the resistors did help, and the optimum capacitor value at 
C25, C26, C27 and C28 turned out to be 4.7nF. The second and fifth 
harmonics were just 80dB below the fundamental and the third 91dB down. 
Not dramatically good, but respectable.

Other changes were less succesful - the current nmirror approach does 
suffer from the need to split the waveform in order to generate the 
asmplitude correction waveform and minimising the 2usec wide switching 
spikes that show up at cross-over is what it takes to get it to work 
tolerably well

I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer 
from parasitic oscillations in LTSpice 24, so it should simulate 
tolerably fast.

Version 4
SHEET 1 3608 920
WIRE -1936 -2432 -2320 -2432
WIRE -1696 -2432 -1936 -2432
WIRE -1360 -2432 -1696 -2432
WIRE -1200 -2432 -1360 -2432
WIRE -1104 -2432 -1200 -2432
WIRE -736 -2432 -1104 -2432
WIRE -320 -2432 -736 -2432
WIRE 208 -2432 -320 -2432
WIRE 336 -2432 208 -2432
WIRE 672 -2432 336 -2432
WIRE -736 -2416 -736 -2432
WIRE -320 -2416 -320 -2432
WIRE 208 -2416 208 -2432
WIRE -1696 -2384 -1696 -2432
WIRE 3472 -2272 -1616 -2272
WIRE 3248 -2224 -1056 -2224
WIRE 448 -2192 -1776 -2192
WIRE -1776 -2160 -1776 -2192
WIRE -1360 -2160 -1360 -2432
WIRE -1200 -2160 -1200 -2432
WIRE -736 -2160 -736 -2352
WIRE -656 -2160 -736 -2160
WIRE -320 -2160 -320 -2352
WIRE -176 -2160 -320 -2160
WIRE -1616 -2144 -1616 -2272
WIRE -1056 -2144 -1056 -2224
WIRE 208 -2144 208 -2352
WIRE 336 -2144 208 -2144
WIRE -1920 -2032 -2048 -2032
WIRE -1888 -2032 -1920 -2032
WIRE -1776 -2032 -1776 -2080
WIRE -1776 -2032 -1824 -2032
WIRE -1200 -2032 -1200 -2080
WIRE -1056 -2032 -1056 -2064
WIRE -1056 -2032 -1200 -2032
WIRE -1776 -2000 -1776 -2032
WIRE -320 -2000 -320 -2160
WIRE -1360 -1984 -1360 -2080
WIRE -1200 -1984 -1200 -2032
WIRE -736 -1984 -736 -2160
WIRE -2048 -1968 -2048 -2032
WIRE 336 -1968 336 -2144
WIRE 672 -1968 672 -2432
WIRE -1280 -1936 -1296 -1936
WIRE -1264 -1936 -1280 -1936
WIRE 2048 -1920 1840 -1920
WIRE 2256 -1920 2048 -1920
WIRE 1472 -1904 1168 -1904
WIRE 1632 -1904 1472 -1904
WIRE 336 -1888 336 -1904
WIRE -576 -1872 -912 -1872
WIRE -32 -1872 -496 -1872
WIRE 1840 -1872 1840 -1920
WIRE -1920 -1856 -1920 -2032
WIRE -1888 -1856 -1920 -1856
WIRE -1776 -1856 -1776 -1920
WIRE -1776 -1856 -1824 -1856
WIRE -1280 -1856 -1280 -1936
WIRE -1200 -1856 -1200 -1888
WIRE -1200 -1856 -1280 -1856
WIRE 1168 -1856 1168 -1904
WIRE -1200 -1840 -1200 -1856
WIRE 2048 -1824 2000 -1824
WIRE 2256 -1824 2256 -1920
WIRE 2256 -1824 2128 -1824
WIRE -128 -1808 -272 -1808
WIRE -32 -1808 -32 -1872
WIRE -32 -1808 -64 -1808
WIRE -1360 -1792 -1360 -1888
WIRE -1360 -1792 -2160 -1792
WIRE -1264 -1792 -1360 -1792
WIRE -912 -1792 -912 -1872
WIRE -864 -1792 -912 -1792
WIRE -544 -1792 -784 -1792
WIRE 672 -1776 672 -1904
WIRE 864 -1776 672 -1776
WIRE 2256 -1776 2256 -1824
WIRE 2384 -1776 2256 -1776
WIRE 2528 -1776 2464 -1776
WIRE 2592 -1776 2528 -1776
WIRE 2896 -1776 2672 -1776
WIRE 2960 -1776 2896 -1776
WIRE 3184 -1776 3040 -1776
WIRE -544 -1760 -544 -1792
WIRE 1376 -1760 1328 -1760
WIRE 1632 -1760 1632 -1904
WIRE 1632 -1760 1456 -1760
WIRE -1776 -1744 -1776 -1856
WIRE -2160 -1728 -2160 -1792
WIRE 3184 -1728 3184 -1776
WIRE -2320 -1712 -2320 -2432
WIRE -272 -1712 -272 -1808
WIRE -128 -1712 -272 -1712
WIRE -32 -1712 -32 -1808
WIRE -32 -1712 -64 -1712
WIRE 2528 -1712 2528 -1776
WIRE -2352 -1696 -2400 -1696
WIRE -2320 -1696 -2320 -1712
WIRE -2224 -1680 -2288 -1680
WIRE -2352 -1664 -2480 -1664
WIRE 1744 -1648 1488 -1648
WIRE 2160 -1648 1744 -1648
WIRE -912 -1632 -912 -1792
WIRE -848 -1632 -912 -1632
WIRE -544 -1632 -544 -1680
WIRE -544 -1632 -784 -1632
WIRE -1776 -1616 -1776 -1664
WIRE -1696 -1616 -1696 -2304
WIRE -1696 -1616 -1776 -1616
WIRE -1200 -1616 -1200 -1744
WIRE -1200 -1616 -1440 -1616
WIRE -1072 -1616 -1200 -1616
WIRE -912 -1616 -912 -1632
WIRE -912 -1616 -992 -1616
WIRE -272 -1616 -272 -1712
WIRE -144 -1616 -272 -1616
WIRE -32 -1616 -32 -1712
WIRE -32 -1616 -64 -1616
WIRE 2160 -1616 2160 -1648
WIRE 1488 -1600 1488 -1648
WIRE 2000 -1600 2000 -1824
WIRE 2128 -1600 2000 -1600
WIRE -2400 -1584 -2400 -1696
WIRE -2256 -1584 -2400 -1584
WIRE -2160 -1584 -2160 -1632
WIRE -2160 -1584 -2256 -1584
WIRE -1776 -1584 -1776 -1616
WIRE -1776 -1584 -2016 -1584
WIRE -544 -1584 -544 -1632
WIRE -512 -1584 -544 -1584
WIRE -432 -1584 -448 -1584
WIRE -272 -1584 -272 -1616
WIRE -272 -1584 -352 -1584
WIRE 1328 -1584 1328 -1760
WIRE 1456 -1584 1328 -1584
WIRE 2256 -1584 2256 -1776
WIRE 2256 -1584 2192 -1584
WIRE 2528 -1584 2528 -1632
WIRE 1632 -1568 1632 -1760
WIRE 1632 -1568 1520 -1568
WIRE 1680 -1568 1632 -1568
WIRE 1840 -1568 1840 -1808
WIRE 1840 -1568 1760 -1568
WIRE 1888 -1568 1840 -1568
WIRE 2096 -1568 1968 -1568
WIRE 2128 -1568 2096 -1568
WIRE -176 -1552 -176 -2160
WIRE 1008 -1552 976 -1552
WIRE 1168 -1552 1168 -1792
========== REMAINDER OF ARTICLE TRUNCATED ==========