Path: ...!weretis.net!feeder9.news.weretis.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!nnrp.usenet.blueworldhosting.com!.POSTED!not-for-mail
From: "Edward Rawde" <invalid@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: 80dB now but still needs improvement at 1KHz
Date: Tue, 5 Nov 2024 21:39:44 -0500
Organization: BWH Usenet Archive (https://usenet.blueworldhosting.com)
Lines: 480
Message-ID: <vgekth$1anu$1@nnrp.usenet.blueworldhosting.com>
References: <vg9h7b$277o$1@nnrp.usenet.blueworldhosting.com> <vg9pnu$ekhh$1@solani.org> <vga6jh$suru$1@dont-email.me> <vgatph$46a$1@nnrp.usenet.blueworldhosting.com> <vgbv7l$177js$3@dont-email.me>
Injection-Date: Wed, 6 Nov 2024 02:39:45 -0000 (UTC)
Injection-Info: nnrp.usenet.blueworldhosting.com;
	logging-data="43774"; mail-complaints-to="usenet@blueworldhosting.com"
Cancel-Lock: sha1:Oifu9c35HSZt0FHOQIQ//sJ2mgQ= sha256:H+iOVnUK8qTt8f6OHiBVjMhI8OgU/rUdMTCVudMMNfU=
	sha1:7pMW41v22JrhZbyKXwUKcOvbPlw= sha256:sEDd+vLEZG70s/OVmTBS2BeQATm1eXkJFjAD6733d3Q=
X-MSMail-Priority: Normal
X-RFC2646: Format=Flowed; Response
X-Priority: 3
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
Bytes: 14857

"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vgbv7l$177js$3@dont-email.me...
> On 5/11/2024 3:46 am, Edward Rawde wrote:
>> "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vga6jh$suru$1@dont-email.me...
>>> On 4/11/2024 5:31 pm, Jan Panteltje wrote:
>>>> On a sunny day (Sun, 3 Nov 2024 23:06:04 -0500) it happened "Edward Rawde"
>>>> <invalid@invalid.invalid> wrote in
>>>> <vg9h7b$277o$1@nnrp.usenet.blueworldhosting.com>:
>>>>
>>>>> Simulation isn't fast but if you let it complete and do an FFT on the last 30 seconds, it's 80dB down at all unwanted
>>>>> harmonics.
>>>>> There do however seem to be unwanted sidebands close in either side of 1KHz
>>>>> Any suggestions for improvement?
>>>>
>>>> Publish a circuit diagram.
>>>> Not that hard to make !
>>>
>>> He did. The .asc file is a circuit diagram. I've looked at it and run the simulation - if only for 200 seconds rather than 300
>>> seconds.
>>>
>>> The FFT says that sine wave is as good as he claims.
>>>
>>> The circuit diagram  doesn't make it clear what it's various parts are there to do - it makes sense to group the components in a
>>> way that lets somebody looking at the circuit diagram get some feel for what the components are doing.
>>>
>>> And it you are using the LT1994 it makes sense to read the data sheet carefully enough to notice that the Icom pin 2 should be
>>> bypassed with at least 100nF to ground.
>>>
>>> https://www.analog.com/media/en/technical-documentation/data-sheets/1994fb.pdf
>>
>> Yes there's no way I would use a part without reading the data sheet.
>> Pass 1 fount the 0.1uF but I hadn't got around to adding it.
>> Pass 2 found that I couldn't go above +/- 6V
>> Pass 3 which I haven't done yet would take a lot more time and I probably won't do it because I doubt I'll be able to build this 
>> for
>> real.
>>
>> Please see also my reply to Jan.
>>
>>>
>>> John May's circuit makes it clear that the second FET isn't strictly necessary. There are cheaper ways of getting rid of the
>>> even-order harmonics.
>>
>> Does his circuit have better performance?
>
> The version I got privately certainly did.
>
>> Just curious, it's not a competition.
>
> Actually, I've decided that the second FET is a bad idea. Two different FETs need two different gate drive voltages to give the 
> right channel resistance, and the only guide you've got to that is the amplitude of the single sine wave you are producing. A 
> large number of different pairs of FET gate drive voltages could give you the same stable amplitude.
>
> If you monitored the second harmonic component of the output you would have a second independent output which could let you 
> optimise both gate dries at the same time, but that would be an unnecessary refinement.
>

Now approacing 90dB if you believe the simulation with with this experimental circuit.
You'll want to find something else to do while it simulates.
How to inprove it further?

Version 4
SHEET 1 2196 932
WIRE -160 -752 -208 -752
WIRE 16 -752 -80 -752
WIRE 128 -752 16 -752
WIRE 288 -752 208 -752
WIRE -208 -688 -208 -752
WIRE -128 -688 -208 -688
WIRE 80 -688 -64 -688
WIRE 128 -688 80 -688
WIRE 288 -688 288 -752
WIRE 288 -688 192 -688
WIRE 80 -656 80 -688
WIRE 16 -640 16 -752
WIRE 16 -544 16 -576
WIRE 80 -544 80 -576
WIRE 16 -464 16 -480
WIRE 80 -448 48 -448
WIRE 288 -448 288 -688
WIRE 288 -448 80 -448
WIRE -208 -432 -208 -688
WIRE -16 -432 -208 -432
WIRE 192 -416 48 -416
WIRE 240 -416 192 -416
WIRE 368 -416 320 -416
WIRE 432 -416 368 -416
WIRE 512 -416 432 -416
WIRE 624 -416 512 -416
WIRE -208 -384 -208 -432
WIRE 16 -384 16 -400
WIRE 368 -368 368 -416
WIRE 80 -352 80 -448
WIRE 192 -352 192 -416
WIRE 432 -352 432 -416
WIRE 512 -352 512 -416
WIRE 624 -352 624 -416
WIRE -208 -272 -208 -304
WIRE -208 -272 -304 -272
WIRE -208 -240 -208 -272
WIRE 80 -240 80 -272
WIRE 192 -240 192 -288
WIRE 432 -240 432 -288
WIRE 512 -224 512 -288
WIRE 624 -224 624 -288
WIRE 368 -192 368 -288
WIRE 368 -192 -16 -192
WIRE -304 -176 -304 -272
WIRE -336 -128 -368 -128
WIRE -208 -128 -208 -160
WIRE -208 -128 -240 -128
WIRE -192 -128 -208 -128
WIRE 144 -128 -192 -128
WIRE 288 -128 224 -128
WIRE 352 -128 288 -128
WIRE 512 -128 512 -144
WIRE 512 -128 432 -128
WIRE -368 -48 -368 -128
WIRE -320 -48 -368 -48
WIRE -192 -48 -192 -128
WIRE -192 -48 -240 -48
WIRE 288 -16 288 -128
WIRE 288 -16 64 -16
WIRE 352 -16 288 -16
WIRE 512 -16 512 -128
WIRE 512 -16 432 -16
WIRE -368 0 -368 -48
WIRE 144 48 144 32
WIRE 64 96 64 -16
WIRE 112 96 64 96
WIRE 512 96 512 -16
WIRE 512 96 272 96
WIRE -32 128 -112 128
WIRE -16 128 -16 -192
WIRE -16 128 -32 128
WIRE 112 128 -16 128
WIRE -336 144 -416 144
WIRE -272 144 -336 144
WIRE 624 144 624 -144
WIRE 656 144 624 144
WIRE 768 144 720 144
WIRE 848 144 768 144
WIRE -112 160 -112 128
WIRE 112 160 64 160
WIRE 624 160 624 144
WIRE 624 160 272 160
WIRE -416 192 -416 144
WIRE -272 208 -272 144
WIRE 144 224 144 208
WIRE 848 240 848 144
WIRE -112 256 -112 224
WIRE 64 272 64 160
WIRE 160 272 64 272
WIRE 256 272 160 272
WIRE 352 272 320 272
WIRE 512 272 512 96
WIRE 512 272 432 272
WIRE 64 288 64 272
WIRE 160 288 160 272
WIRE 512 320 512 272
WIRE 624 320 624 160
WIRE -416 368 -416 272
WIRE -416 368 -496 368
WIRE -496 384 -496 368
WIRE -416 384 -416 368
WIRE -272 384 -272 272
WIRE -272 384 -416 384
WIRE 64 384 64 368
WIRE 160 384 160 352
WIRE 160 384 64 384
WIRE 64 416 64 384
WIRE 848 416 848 320
WIRE -32 448 -32 128
WIRE -416 464 -416 384
WIRE 144 464 96 464
WIRE 256 464 224 464
WIRE 368 464 320 464
WIRE -272 480 -272 384
WIRE 512 480 512 400
WIRE 624 480 624 400
========== REMAINDER OF ARTICLE TRUNCATED ==========