suggested circuits/pcbs to sum positive CV

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ndkent
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suggested circuits/pcbs to sum positive CV

Post by ndkent » Sun Apr 04, 2021 12:50 pm

I've got a couple positive CVs I'd like to sum. I'd like to power from +15v (so no minus rail)

any simple circuits or pcb suggestions?

thanks!

Don T
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Re: suggested circuits/pcbs to sum positive CV

Post by Don T » Sun Apr 04, 2021 1:50 pm

Almost any basic DC-coupled mixer circuit would work

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ndkent
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Re: suggested circuits/pcbs to sum positive CV

Post by ndkent » Sun Apr 04, 2021 2:33 pm

What I've been finding also requires a negative supply, trying to find something simple that just runs on +

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bgreeves
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Re: suggested circuits/pcbs to sum positive CV

Post by bgreeves » Sun Apr 04, 2021 2:34 pm

With unipolar power, this isn't quite as trivial as it usually is with bipolar power.

Unless you want to bother creating a 7.5V center reference, using op-amp's in inverting configuration is pretty much out of the question AFAIK.

If you have N signals you want to sum, and they will always be connected, then you can do a non-inverting summer by combining a voltage averager with a non-inverting op-amp with gain of N: https://www.allaboutcircuits.com/textbo ... -circuits/.

Unipolar power circuits are a bit out of my range of expertise (if I can even claim any expertise with electronics). I envision you may have problems reaching 0V if you don't use a rail-to-rail op-amp.

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Luka
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Re: suggested circuits/pcbs to sum positive CV

Post by Luka » Sun Apr 04, 2021 4:04 pm


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guest
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Re: suggested circuits/pcbs to sum positive CV

Post by guest » Sun Apr 04, 2021 7:29 pm

the link that bgreeves suggested is a good way of doing it. there are 2 things to watch out for, though:

1. can your opamps handle 0V to 12V (or 15V) signals at the input and outputs (rail to rail)?
2. are all of your inputs either coming from normalled jacks or other opamp stages? a floating jack will change the gain equation, and scale all the CVs differently. this can sometime be handy, as it automatically reduces the output gain with each new signal plugged in, so the circuit is less likely to saturate. generally this isnt what you want with CVs, though.

if either of those arent true, then you should consider doing 2 inverting stages with the non-inverting pin at 7.5V for both opamps. you will still need a rail to rail output opamp (or at least the bottom rail) if you want the signals to go that low.
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ndkent
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Re: suggested circuits/pcbs to sum positive CV

Post by ndkent » Sun Apr 04, 2021 8:40 pm

thanks bgreeves - and those who posted

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