 # How To Multiply Two Voltages/currents Together

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How can you multiply two voltages together? I'm working on a pedal that requires taking two input voltages and outputting the algebraic product of the two. This is not the same as multiplying a single voltage times a scalar value.

Also, is it possible to do the same thing, but with current instead of voltage?

I imagine either of them would involve using a transistor to have one input control the other, but I can't figure how exactly to do it.

For clarity, the device would follow: Vo = V1 x V2. Vo is the output and V1 and V2 are inputs.

It might also be helpful if someone has a method of dividing two voltages or currents.

I understand that there may be a problem with units; you would end up getting volts squared or amps squared. But maybe if there could be some sort of device that follows Vo = (V1xV2)/V3............

any thoughts on how to do any of this?

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How can you multiply two voltages together? I'm working on a pedal that requires taking two input voltages and outputting the algebraic product of the two. This is not the same as multiplying a single voltage times a scalar value.

Also, is it possible to do the same thing, but with current instead of voltage?

I imagine either of them would involve using a transistor to have one input control the other, but I can't figure how exactly to do it.

For clarity, the device would follow: Vo = V1 x V2. Vo is the output and V1 and V2 are inputs.

It might also be helpful if someone has a method of dividing two voltages or currents.

I understand that there may be a problem with units; you would end up getting volts squared or amps squared. But maybe if there could be some sort of device that follows Vo = (V1xV2)/V3............

any thoughts on how to do any of this?

Interesting, I bet there are proper chips that do that, but the nearset thing i can think of, gear wise, is a tremelo circuit where the sound signal is amplified by a factor that varies with time, based on the oscillations of the tremelo. You could check out how they work.

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It almost sounds like you are designing a differential amplifier circuit or something like that.

A differential pair amplifies the difference between two input signals/voltages, and has an inverted and a non-inverted output. The DC offset bias on each input signal affects how the output waveforms look. That seems to be basically the same thing you are trying to accomplish...

Edited by Paul Marossy
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It almost sounds like you are designing a differential amplifier circuit or something like that.

A differential pair amplifies the difference between two input signals/voltages, and has an inverted and a non-inverted output. The DC offset bias on each input signal affects how the output waveforms look. That seems to be basically the same thing you are trying to accomplish...

seems like youre describing an opamp. but no, an opamp can only add/subtract signals together, then multiply them by a constant. that is different from multiplying the two together.

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It almost sounds like you are designing a differential amplifier circuit or something like that.

A differential pair amplifies the difference between two input signals/voltages, and has an inverted and a non-inverted output. The DC offset bias on each input signal affects how the output waveforms look. That seems to be basically the same thing you are trying to accomplish...

seems like youre describing an opamp. but no, an opamp can only add/subtract signals together, then multiply them by a constant. that is different from multiplying the two together.

Yeah, I guess that would be a dual opamp, wouldn't it?! Doh! Hmm... not sure on that one. I'm intrigued by this concept. I'll do some asking around.

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Well, it's been almost a year since I covered this in my AP physics class but if I remember correctly, you cannot multiply two voltages together. You can only add voltages in series or add the reciprocal (1/V) in parallel (why parallel wired pickups are quieter than series).

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Well, it's been almost a year since I covered this in my AP physics class but if I remember correctly, you cannot multiply two voltages together. You can only add voltages in series or add the reciprocal (1/V) in parallel (why parallel wired pickups are quieter than series).

Well that covers series and parallel connections, but I'm asking about a possibly different connection, probably involving a transistor or opamp, that does multiply the two together.

the idea i had originally was to connect one input to a transistor collector, and the other input to the base somehow. but the method in which you connect it gets pretty tricky. can anyone figure it out?

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Take a look at this IC chip and see if it will do what you want to do:

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Take a look at this IC chip and see if it will do what you want to do:

i havent read the whole document yet, but by the looks of it, i can make this work!

how did you find this chip? if you dont mind me asking

is there some sort of chip database that you went to?

and it's analog! awesome!

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Take a look at this IC chip and see if it will do what you want to do:

i havent read the whole document yet, but by the looks of it, i can make this work!

how did you find this chip? if you dont mind me asking

is there some sort of chip database that you went to?

and it's analog! awesome!

Cool, glad I could help. I asked your [re-phrased] question at another forum I am part of to get that answer. I didn't know that sort of IC chip existed, so this one is going in the mental rolodex! ##### Share on other sites

Cool, glad I could help. I asked your [re-phrased] question at another forum I am part of to get that answer. I didn't know that sort of IC chip existed, so this one is going in the mental rolodex! and note, the key is the part about dividing the product by 10V. That way, the output unit would be V, not V^2. Or else scientifically it wouldnt work.

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