[sdiy] Waveshapers based on Max-min operations (Re: Simple circuit challenge: |a-b|)

[houshu at muj.biglobe.ne.jp]

Hello Rutgers and List,

I designed variations of Max-min based waveshapers, which may be of your 
interests.
They are quite simple and quite precise.

Explanations are in Japanese, but I guess schematics and waveforms are 
sufficient information for you.

Full-Wave Rectifiers (Absolute Value) Based on Max-Min Operation.
https://understandcircuit.seesaa.net/article/505024372.html

Single Opamp Wavefolder with Folding Threshold Control.
https://understandcircuit.seesaa.net/article/505024822.html

Wave Multiplier with Folding Threshold Control.
https://understandcircuit.seesaa.net/article/505024858.html

Absolute Value of Difference with Single OP Amp.
https://understandcircuit.seesaa.net/article/503838897.html

Best,
Osamu Sam HOSHUYAMA
Kawasaki, JAPAN



------ Original Message ------
差出人: "Rutger Vlek" <rutgervlek at gmail.com>
To: "houshu at muj.biglobe.ne.jp" <houshu at muj.biglobe.ne.jp>
Cc: "SDIY List" <Synth-diy at synth-diy.org>
送信済み: 月曜日, 2024/4/1  19:32
件名: Re: [sdiy] Simple circuit challenge: |a-b|

Thanks everyone for the suggestions!

I agree with Roman, the Graetz bridge solution is very elegant, thanks 
for sharing Osamu! Will keep you posted on progress with this circuit. 
If the prototype works as expected, I'll share the details here on the 
list.


Rutger


Op do 28 mrt 2024 om 03:43 schreef houshu at muj.biglobe.ne.jp 
<houshu at muj.biglobe.ne.jp>:

      Hello Rutger and List,

Here is my solution.
|a-b| = Max(a,b) - min(a,b).
If output offset is acceptable, we can omit D5, D6, and R7.
Impedance of inputs should be low.  When one of inputs is open, output 
is a little distorted.
Sam HOSHUYAMAKawasaki, Japan.



------ Original Message ------
差出人: "Rutger Vlek via Synth-diy" <synth-diy at synth-diy.org>
To: "SDIY List" <Synth-diy at synth-diy.org>
送信済み: 金曜日, 2024/3/22  04:50
件名: [sdiy] Simple circuit challenge: |a-b|

Dear list,

while hobbying on an experimental design, I'm looking for a simple 
analog circuit to give me the absolute value of the difference between 
two signals (mathematically written as |a-b|).


I already have a working circuit, but it's rather big for my needs. It 
uses an inverting opamp to invert signal A, followed by a bog-standard 
full wave precision rectifier circuit where -A and B are summed together 
and being rectified. The total is 3 opamps, 2 diodes and 9 resistors. As 
I need to repeat the circuit many times in the final application, I'm 
wondering: is there anything simpler that can do this?


Requirements:
- working across full audio range
- distortion as consequence of diode drops is no problem (might even be 
beneficial!)


Many thanks for any suggestions!


Regards,


Rutger

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