Re: cheap analog square function?

From	Christopher Howard <christopher@librehacker.com>
Newsgroups	sci.electronics.design
Subject	Re: cheap analog square function?
Date	2026-02-10 07:49 -0900
Organization	A noiseless patient Spider
Message-ID	<87y0l0a6i5.fsf@librehacker.com> (permalink)
References	<877bslbhl7.fsf@librehacker.com> <10mfed8$3lj5g$2@paganini.bofh.team>

Show all headers | View raw

> Standard apprach for low-accuracy approximation is diode-resistor
> network.  But such network gets inpractically large if you need
> good approximation.

Thank you. Looking at all the suggestions put forward, it seems like —
for my application — that just getting the AD633 might be best choice.
My analog computer is short one multiplier for a simulation I wanted to
play with, and I wonder if there was some easy trick to get a reasonably
accurate square function without getting a decent multiplier. In a lot
of basic physics simulations, one has to square velocity to get
things like drag or lift forces.

Line approximation with a resistor-diode has some appeal. Maybe it could
be accurate enough for my little educational experiments? I think, to
pull it off, I would need to use trim pots — two per segment, for the
biasing and the attenuating.

The schematic from the neurological paper seemed to be a line
approximation solution with some of the diodes in the op amp feedback. I
didn't try to get the whole research paper so I'm not sure how one would
work out the correct resistor values.

I downloaded the information on the MC1496-D and LM13700. I see the
basic idea is that these chips also produce products of signals, but
beyond that I can't make any intelligent comments at present. My analog
computer is usually dealing with signals in the range of a few hundred
Hz up to a few kHz. I am curious if maybe something could be done with
the gain control pin on the LM386 chip (I have quite a few of those). It
looks like, using a series RC network, that the gain can be set anywhere
from 20 to 200.

-- 
Christopher Howard

Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

cheap analog square function? Christopher Howard <christopher@librehacker.com> - 2026-02-09 14:52 -0900
  Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-09 16:47 -0800
  Re: cheap analog square function? Don Y <blockedofcourse@foo.invalid> - 2026-02-09 17:50 -0700
  Re: cheap analog square function? "Edward Rawde" <invalid@invalid.invalid> - 2026-02-09 20:03 -0500
  Re: cheap analog square function? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-02-10 02:05 +0000
  Re: cheap analog square function? Jan Panteltje <alien@comet.invalid> - 2026-02-10 05:50 +0000
    Re: cheap analog square function? bitrex <user@example.net> - 2026-02-10 03:39 -0500
  Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-10 18:05 +1100
    Re: cheap analog square function? John R Walliker <jrwalliker@gmail.com> - 2026-02-10 08:41 +0000
      Re: cheap analog square function? bitrex <user@example.net> - 2026-02-10 03:46 -0500
        Re: cheap analog square function? bitrex <user@example.net> - 2026-02-10 03:49 -0500
  Re: cheap analog square function? antispam@fricas.org (Waldek Hebisch) - 2026-02-10 14:12 +0000
    Re: cheap analog square function? Christopher Howard <christopher@librehacker.com> - 2026-02-10 07:49 -0900
      Re: cheap analog square function? Don Y <blockedofcourse@foo.invalid> - 2026-02-10 11:40 -0700
      Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-10 11:39 -0800
        Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-11 23:38 +1100
          Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-11 07:56 -0800
            Re: cheap analog square function? Buzz McCool <buzz_mccool@yahoo.com> - 2026-02-11 09:30 -0800
              Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-11 09:38 -0800
                Re: cheap analog square function? liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2026-02-11 18:52 +0000
                Re: cheap analog square function? bitrex <user@example.net> - 2026-02-11 14:22 -0500
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-11 12:14 -0800
                Re: cheap analog square function? bitrex <user@example.net> - 2026-02-11 15:35 -0500
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-11 13:04 -0800
                Re: cheap analog square function? bitrex <user@example.net> - 2026-02-11 16:35 -0500
                Re: cheap analog square function? Lasse Langwadt <llc@fonz.dk> - 2026-02-11 21:41 +0100
                Re: cheap analog square function? Jeroen Belleman <jeroen@nospam.please> - 2026-02-11 22:49 +0100
            Re: cheap analog square function? Lasse Langwadt <llc@fonz.dk> - 2026-02-11 21:37 +0100
            Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-12 17:36 +1100
              Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-12 10:19 -0800
                Re: cheap analog square function? Lasse Langwadt <llc@fonz.dk> - 2026-02-12 21:05 +0100
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-12 14:12 -0800
                Re: cheap analog square function? Lasse Langwadt <llc@fonz.dk> - 2026-02-12 23:39 +0100
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-12 15:19 -0800
                Re: cheap analog square function? Don Y <blockedofcourse@foo.invalid> - 2026-02-12 18:13 -0700
                Re: cheap analog square function? Gerhard Hoffmann <dk4xp@arcor.de> - 2026-02-13 00:38 +0100
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-12 16:09 -0800
                Re: cheap analog square function? Gerhard Hoffmann <dk4xp@arcor.de> - 2026-02-13 02:42 +0100
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-13 09:30 -0800
                Re: cheap analog square function? Jan Panteltje <alien@comet.invalid> - 2026-02-14 06:14 +0000
                Re: cheap analog square function? Glen Walpert <nospam@null.void> - 2026-02-14 14:18 +0000
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-14 07:51 -0800
                Re: cheap analog square function? Jan Panteltje <alien@comet.invalid> - 2026-02-15 06:27 +0000
                Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-14 07:47 -0800
                Re: cheap analog square function? Jan Panteltje <alien@comet.invalid> - 2026-02-15 06:50 +0000
                Re: cheap analog square function? mas@example.com - 2026-02-16 07:38 +0000
                Re: cheap analog square function? Jan Panteltje <alien@comet.invalid> - 2026-02-16 08:49 +0000
              Re: cheap analog square function? legg <legg@nospam.magma.ca> - 2026-02-14 08:57 -0500
  Re: cheap analog square function? piglet <erichpwagner@hotmail.com> - 2026-02-12 21:37 +0000
    Re: cheap analog square function? Christopher Howard <christopher@librehacker.com> - 2026-02-13 06:40 -0900
      Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-13 08:34 -0800
        Re: cheap analog square function? bitrex <user@example.net> - 2026-02-13 13:00 -0500
          Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-13 10:52 -0800
        Re: cheap analog square function? bitrex <user@example.net> - 2026-02-13 13:01 -0500
      Re: cheap analog square function? piglet <erichpwagner@hotmail.com> - 2026-02-13 19:36 +0000
        Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-13 12:06 -0800
          Re: cheap analog square function? piglet <erichpwagner@hotmail.com> - 2026-02-13 20:42 +0000
            Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-15 12:43 -0800
        Re: cheap analog square function? Christopher Howard <christopher@librehacker.com> - 2026-02-16 09:36 -0900
          Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-18 00:03 +1100
            Re: cheap analog square function? john larkin <jl@glen--canyon.com> - 2026-02-17 08:06 -0800
        Re: cheap analog square function? Christopher Howard <christopher@librehacker.com> - 2026-02-16 13:08 -0900
          Re: cheap analog square function? piglet <erichpwagner@hotmail.com> - 2026-02-17 11:40 +0000
            Re: cheap analog square function? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-02-17 12:34 -0500
              Re: cheap analog square function? Gerhard Hoffmann <dk4xp@arcor.de> - 2026-02-17 18:57 +0100
                Re: cheap analog square function? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-02-17 18:18 +0000
                Re: cheap analog square function? Gerhard Hoffmann <dk4xp@arcor.de> - 2026-02-17 19:39 +0100
                Re: cheap analog square function? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-02-17 14:00 -0500
                Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-18 15:10 +1100
              Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-18 14:43 +1100
          Re: cheap analog square function? Bill Sloman <bill.sloman@ieee.org> - 2026-02-18 01:43 +1100
      Re: cheap analog square function? Jan Panteltje <alien@comet.invalid> - 2026-02-14 05:53 +0000

csiph-web