Warning: mysqli::__construct(): (HY000/1203): User howardkn already has more than 'max_user_connections' active connections in D:\Inetpub\vhosts\howardknight.net\al.howardknight.net\includes\artfuncs.php on line 21
Failed to connect to MySQL: (1203) User howardkn already has more than 'max_user_connections' active connectionsPath: ...!3.eu.feeder.erje.net!2.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: john larkin Newsgroups: sci.electronics.design Subject: Re: AF Osc AGC alternatives to lamp/thermistor/FET Date: Mon, 21 Oct 2024 12:22:00 -0700 Organization: A noiseless patient Spider Lines: 54 Message-ID: References: <4k8ahjdivttskhs7c3nlgtao60irbk5fsi@4ax.com> <67154b03$2$1780$882e4bbb@reader.netnews.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Mon, 21 Oct 2024 21:20:21 +0200 (CEST) Injection-Info: dont-email.me; posting-host="ba5414ce5d4141e2c724c35284e110b3"; logging-data="1131349"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1906Hi9m2Jrdbw2IzsKO9wL" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:ioas+OrceJuxOsmZ/osKQRZ7YwM= Bytes: 3226 On Sun, 20 Oct 2024 19:25:08 -0000 (UTC), Cursitor Doom wrote: >On Sun, 20 Oct 2024 11:42:27 -0700, john larkin wrote: > >> On Sun, 20 Oct 2024 14:25:33 -0400, bitrex wrote: >> >>>On 10/20/2024 11:38 AM, john larkin wrote: >>>> On Sun, 20 Oct 2024 14:15:19 +0100, piglet >>>> wrote: >>>> >>>>> Yesterday in the thread "Random thoughts on sinewave oscillators" I >>>>> posted a LT Spice wirelist showing amplitude levelling without fet, >>>>> ntc thermistor or ptc filament instead using current steering long >>>>> tail pair - kinda poor mans multiplier. >>>>> >>>>> Here is another alternative, using diode conductance bridge >>>>> "variolosser". >>>>> >>>>> For the full 1960s vibe replace U2 U3 with bjt current sources. >>>> >>>> That's still limiting a Wein bridge, essentially a single-element >>>> resonator. >>>> >>>> If you do the double-integrator type oscillator, you can do gain >>>> control on the first integrator, and then the second one adds 6 >>>> dB/octave harmonic reduction. >>>> >>>> I think you can even get 12 dB/octave harmonic reduction if you do the >>>> amplitude limiter right. 12*3 = 36! >>>> >>>> >>>> >>>There's probably a way to finagle the 4th section of an LM13700 to apply >>>a bias current inversely proportional to the output level into pin IB1, >>>here: >>> >>> >> >> At some point, opamp distortion and slew rate will usually dominate THD. >> I'd guess that the LM13700 isn't very good. >> >> It might be OK as the small-influence AGC gain tweak, ahead of two good >> integrating opamps. > >At the cost of adding another component, how about adding another opamp >solely to regulate the output signal level? Say you want 2V p-p output, >sample some of the output, rectify it and compare it to a reference level >which is applied to the other opamp input. >Just my 2c. You still need a multiplier of some sort to twaek loop gain. And multipliers are nonlinear!