Differential amplifier 0 to 5v signal input with -10 to +10v output

Discussion in 'General Electronics Chat' started by cj9, Nov 23, 2011.

1. cj9 Thread Starter New Member

Nov 23, 2011
3
0
Hi,

I'm trying to drive a galvanometer which needs a differential input. It's not well documented (galvo board), but I tried driving it with a differential input from a DRV134, which doesn't work properly. The output of the
I can't work out what's going on.

Instead I'm hoping to use an op amp to drive it by putting -10 to 10v on the +ve pin and tying the -ve pin to ground.

The only problem is that I can't find a working circuit anywhere that uses an op amp to convert 0-5v to -10-10v, could anyone help me with this please?

2. nomurphy AAC Fanatic!

Aug 8, 2005
567
12
For DC: by using two op amps from the same input, one that is non-inverting and one that is inverting, both with a gain of 2; then the output of one will go from 0 to +10V while the other goes from 0 to -10V.

If you are dealing with a high enough AC frequency (audio), by cap coupling the 0V-5V input to an op amp it will become +/- 2.5V; with a gain of 4 the output will be +/-10V.

3. SgtWookie Expert

Jul 17, 2007
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I did this schematic for someone awhile back.

It converts 0v to +5v, to -5v to +5v; and has both non-inverting and inverting output.
It depends on +V being 10v, as R1 and R2 are summed to be 5v; and that is summed with the feedback resistor R3.

You could change U1b to a noninverting configuration with a gain of 2 to get your desired output.

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4. cj9 Thread Starter New Member

Nov 23, 2011
3
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Thank you for the schematic, it's very helpful. I'll build it up and see if it works!

Just a quick question - what's the selection switch for?

5. SgtWookie Expert

Jul 17, 2007
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As shown, the selector switch connects the galvanometer to the noninverting output.
If it were at the other position, the inverting output would be connected; the red trace would then be at 5v when the input was 0v, and -5v when the input was at 5v.

6. cj9 Thread Starter New Member

Nov 23, 2011
3
0
I see. I have some LM324s on hand, they are designed to "eliminate the need for dual rail power supplies". This means they have ground rather than -ve voltage input. Could you tell me if this circuit can utilise the LM324? It would be helpful as they have 4 amps in each chip. Thanks!

7. t_n_k AAC Fanatic!

Mar 6, 2009
5,448
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If you eliminate the negative supply by replacing it with ground then the op-amp output can't swing below ground. You need a ±10V swing.

8. SgtWookie Expert

Jul 17, 2007
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You can use the LM324, but you must have dual rails; at least ±13v.