<div dir="ltr">Dear Osamu Sam & list,<div><br></div><div>Thanks again for sharing! Using the schematic in your first link, I have simulated your full-wave rectifier in Spice and compared it to a commonly used 2-opamp precision rectifier circuit (Figure 4 on this page <a href="https://sound-au.com/appnotes/an001.htm">https://sound-au.com/appnotes/an001.htm</a>). It seems to perform very well (on 1kHz sine), and seems to even outperform the standard precision rectifier on high frequency accuracy (20kHz sine). This comparison made me wonder about a couple of things though:</div><div><br></div><div>1) Noise performance: probably due to the large 1M resistors around the opamp, the noise performance seems below that of the 2-opamp rectifier. In simulation I could lower the 1Meg resistors around the opamp to 100K, without much apparearant harm to the quality of the output, but benefits to noise performance. What is the reason for the proposed 1M values?</div><div>2) The other circuit: on the bottom of the schematic on your website there's an alternative circuit, with a note "My older design seems a little more precise". In my simulation however, it is much less precise... What did I do wrong?<br></div><div>3) How important is diode matching?<br></div><div>4) How important is voltage accuracy of +V and -V (being tied to the diode bridge via 100K)?</div><div><br></div><div>Otherwise, this is a gem of a circuit that I will definitely keep in mind!</div><div><br></div><div>Rutger</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Op vr 4 okt 2024 om 18:10 schreef Sean Ellis <<a href="mailto:tensiontype@hotmail.com">tensiontype@hotmail.com</a>>:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-7740654136248070075">
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Fantastic ideas, the full wave rectifier is so simple. I dont quite understand how the absolute value circuit works, might have to simulate it.</div>
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Great stuff :)</div>
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<div id="m_-5670077414055187283divRplyFwdMsg" dir="ltr"><span style="font-family:Calibri,sans-serif;font-size:11pt;color:rgb(0,0,0)"><b>From:</b> Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank">synth-diy-bounces@synth-diy.org</a>> on behalf of houshu--- via Synth-diy <<a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a>><br>
</span></div>
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<b>Sent:</b> Thursday, 3 October 2024 4:26 PM<br>
<b>To:</b> Rutger Vlek <<a href="mailto:rutgervlek@gmail.com" target="_blank">rutgervlek@gmail.com</a>><br>
<b>Cc:</b> SDIY List <<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a>><br>
<b>Subject:</b> [sdiy] Waveshapers based on Max-min operations (Re: Simple circuit challenge: |a-b|)</div>
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<div style="font-size:11pt">Hello Rutgers and List,<br>
<br>
I designed variations of Max-min based waveshapers, which may be of your<br>
interests.<br>
They are quite simple and quite precise.<br>
<br>
Explanations are in Japanese, but I guess schematics and waveforms are<br>
sufficient information for you.<br>
<br>
Full-Wave Rectifiers (Absolute Value) Based on Max-Min Operation.<br>
<a href="https://understandcircuit.seesaa.net/article/505024372.html" id="m_-5670077414055187283OWA6addee0a-0862-a8d4-3e98-0ac99424ac37" target="_blank">https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Funderstandcircuit.seesaa.net%2Farticle%2F505024372.html&data=05%7C02%7C%7C5afc30a132a54417a92408dce3fa480b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638635911325026475%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=D6%2FNwIyy2e%2BcKTm86K7dGlVJp5cPQQSLsyVZWkgiwic%3D&reserved=0</a><br>
<br>
Single Opamp Wavefolder with Folding Threshold Control.<br>
<a href="https://understandcircuit.seesaa.net/article/505024822.html" id="m_-5670077414055187283OWA77bafffd-b67a-c983-e503-954b462c4837" target="_blank">https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Funderstandcircuit.seesaa.net%2Farticle%2F505024822.html&data=05%7C02%7C%7C5afc30a132a54417a92408dce3fa480b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638635911325039849%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=GgMfNzMVO3lLjpO3EK6jt%2Bea4St%2FIigMid0XJFjJLtM%3D&reserved=0</a><br>
<br>
Wave Multiplier with Folding Threshold Control.<br>
<a href="https://understandcircuit.seesaa.net/article/505024858.html" id="m_-5670077414055187283OWAcec9d72f-9593-7be1-55ed-b447e915bfb3" target="_blank">https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Funderstandcircuit.seesaa.net%2Farticle%2F505024858.html&data=05%7C02%7C%7C5afc30a132a54417a92408dce3fa480b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638635911325047338%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=mIBfUGhoga38%2B5KyCucJjlSWvQV9IzRaI7PuOzD7c3w%3D&reserved=0</a><br>
<br>
Absolute Value of Difference with Single OP Amp.<br>
<a href="https://understandcircuit.seesaa.net/article/503838897.html" id="m_-5670077414055187283OWA442f81d7-727f-6de3-9a69-a2f37d28c30c" target="_blank">https://apac01.safelinks.protection.outlook.com/?url=https%3A%2F%2Funderstandcircuit.seesaa.net%2Farticle%2F503838897.html&data=05%7C02%7C%7C5afc30a132a54417a92408dce3fa480b%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638635911325054556%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=Ocnt3Bm8RDHy3yANTgwfhtp99Y8Rj9j2bUjhZ7xoxqc%3D&reserved=0</a><br>
<br>
Best,<br>
Osamu Sam HOSHUYAMA<br>
Kawasaki, JAPAN<br>
<br>
<br>
<br>
------ Original Message ------<br>
差出人: "Rutger Vlek" <<a href="mailto:rutgervlek@gmail.com" target="_blank">rutgervlek@gmail.com</a>><br>
To: "<a href="mailto:houshu@muj.biglobe.ne.jp" target="_blank">houshu@muj.biglobe.ne.jp</a>" <<a href="mailto:houshu@muj.biglobe.ne.jp" target="_blank">houshu@muj.biglobe.ne.jp</a>><br>
Cc: "SDIY List" <<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a>><br>
送信済み: 月曜日, 2024/4/1 19:32<br>
件名: Re: [sdiy] Simple circuit challenge: |a-b|<br>
<br>
Thanks everyone for the suggestions!<br>
<br>
I agree with Roman, the Graetz bridge solution is very elegant, thanks<br>
for sharing Osamu! Will keep you posted on progress with this circuit.<br>
If the prototype works as expected, I'll share the details here on the<br>
list.<br>
<br>
<br>
Rutger<br>
<br>
<br>
Op do 28 mrt 2024 om 03:43 schreef <a href="mailto:houshu@muj.biglobe.ne.jp" target="_blank">houshu@muj.biglobe.ne.jp</a><br>
<<a href="mailto:houshu@muj.biglobe.ne.jp" target="_blank">houshu@muj.biglobe.ne.jp</a>>:<br>
<br>
Hello Rutger and List,<br>
<br>
Here is my solution.<br>
|a-b| = Max(a,b) - min(a,b).<br>
If output offset is acceptable, we can omit D5, D6, and R7.<br>
Impedance of inputs should be low. When one of inputs is open, output<br>
is a little distorted.<br>
Sam HOSHUYAMAKawasaki, Japan.<br>
<br>
<br>
<br>
------ Original Message ------<br>
差出人: "Rutger Vlek via Synth-diy" <<a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a>><br>
To: "SDIY List" <<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a>><br>
送信済み: 金曜日, 2024/3/22 04:50<br>
件名: [sdiy] Simple circuit challenge: |a-b|<br>
<br>
Dear list,<br>
<br>
while hobbying on an experimental design, I'm looking for a simple<br>
analog circuit to give me the absolute value of the difference between<br>
two signals (mathematically written as |a-b|).<br>
<br>
<br>
I already have a working circuit, but it's rather big for my needs. It<br>
uses an inverting opamp to invert signal A, followed by a bog-standard<br>
full wave precision rectifier circuit where -A and B are summed together<br>
and being rectified. The total is 3 opamps, 2 diodes and 9 resistors. As<br>
I need to repeat the circuit many times in the final application, I'm<br>
wondering: is there anything simpler that can do this?<br>
<br>
<br>
Requirements:<br>
- working across full audio range<br>
- distortion as consequence of diode drops is no problem (might even be<br>
beneficial!)<br>
<br>
<br>
Many thanks for any suggestions!<br>
<br>
<br>
Regards,<br>
<br>
<br>
Rutger<br>
<br>
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