Is there any multiplier circuit that can work with a maximum supply voltage of +5V?

Thread Starter

asdasd12e12

Joined Nov 24, 2021
48
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I'm using this one but unfortunately i need to supply the op amps around +-16 V while my microcontroller can only output a max of 5V...
 

LowQCab

Joined Nov 6, 2012
2,650
Are You actually building an Analog-Computer ?,
or do You have the terminology mixed-up ?

Do You want more Voltage ?, or a Calculator ?
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.
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DickCappels

Joined Aug 21, 2008
9,513
If you are multiplying very low frequency or DC signals you can get amazing accuracy with a pulse height-width multiplier. One quadrant multipliers can easily work from a single 5V power supply.

What kind of signals do you intend to multiply?
 

MisterBill2

Joined Jan 23, 2018
13,805
This looks a lot like a homework problem.
Also, any multiplication will be over a very limited range because it seems to be depending on diode non-linearity. So it may work with a simulator, I would not useit in a real world application.
 

ericgibbs

Joined Jan 29, 2010
16,803
So it may work with a simulator, I would not useit in a real world application.
Hi Bill,
How can you justify posting such an ill-informed guess.???

That puts doubt in the poster's mind regarding his project.

E
 

MisterBill2

Joined Jan 23, 2018
13,805
The circuit in the first post was copied from a book and it does look like an end of chapter homework problem.
And given the supply requirements and the potential variations in diodes with temperature, it does not seem that it would be useful in an application where the temperature would vary and the opamps were not perfect.
 

Thread Starter

asdasd12e12

Joined Nov 24, 2021
48
If you are multiplying very low frequency or DC signals you can get amazing accuracy with a pulse height-width multiplier. One quadrant multipliers can easily work from a single 5V power supply.

What kind of signals do you intend to multiply?
I'm trying to do a sound level meter where i want to compute its rms with an analog circuit, i need to do the square of that signal. Also i looked up about that pulse height-width multiplier, it looks pretty hard to assemble. It's like an ic that i need to buy?
 

Thread Starter

asdasd12e12

Joined Nov 24, 2021
48
The circuit in the first post was copied from a book and it does look like an end of chapter homework problem.
And given the supply requirements and the potential variations in diodes with temperature, it does not seem that it would be useful in an application where the temperature would vary and the opamps were not perfect.
Do you know any circuit configuration that can do a multiplication operation with a maximum supply voltage of 5V? It doesnt need to be super accurate
 

ericgibbs

Joined Jan 29, 2010
16,803
And given the supply requirements and the potential variations in diodes with temperature, it does not seem that it would be useful in an application where the temperature would vary and the opamps were not perfect.
Hi Bill,
Please post your calculations that support your comments regarding your this poster's circuit's performance.
E
 

DickCappels

Joined Aug 21, 2008
9,513
The True RMS converters mentioned by MisterBill2 are the AD737 and similar. There are now several available.

Notice how little circuitry is actually needed for the converter itself

1667663054510.png

https://www.analog.com/en/technical-articles/ltc1966-true-rms-to-dc-converter.html

These chips are inexpensive considering the circuitry they replace. I used an AD737 to measure RMS audio in a hearing protection circuit. Worked beautifully. Note: Making CAVG larger does a better job of averaging but slows down the settling time of a measurement.
 

LowQCab

Joined Nov 6, 2012
2,650
There are Chips to drive a Bar-or-Dot Array LED Meter,
they are available in Linear or VU-Meter versions,
does that sound like what You want ?
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Thread Starter

asdasd12e12

Joined Nov 24, 2021
48
There are Chips to drive a Bar-or-Dot Array LED Meter,
they are available in Linear or VU-Meter versions,
does that sound like what You want ?
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.
.
The idea was to me to develop an analog circuit, i didnt really wanna skip that and just buy one but i guess in my case i have really no other way because either its to complicated for me to build one or i just dont know how to do it.
 

MisterBill2

Joined Jan 23, 2018
13,805
Another option is to use an averaging circuit instead of calculating true RMS. It will not be as accurate and it will not be true RMS, but depending on the application of the sound level measurement it might be good enough.
Or try the AD737 IC. And I suggest reading whatever application information is available for the AD737 on the AD site. I have found their information to be very useful on several occasions.
 

Thread Starter

asdasd12e12

Joined Nov 24, 2021
48
Another option is to use an averaging circuit instead of calculating true RMS. It will not be as accurate and it will not be true RMS, but depending on the application of the sound level measurement it might be good enough.
Or try the AD737 IC. And I suggest reading whatever application information is available for the AD737 on the AD site. I have found their information to be very useful on several occasions.
An averaging circuit would just be a resistor and a capacitor?
 

MisterBill2

Joined Jan 23, 2018
13,805
An averaging circuit would just be a resistor and a capacitor?
Yes, an averaging circuit could be that simple. There is a good deal of information about averaging circuits as opposed to TRUE RMS circuits. Consider that quite a few VU meters are damped just enough to show an average level. At least the ones intended for broadcast use in times past were.
 
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