Convert Input (0V - +2.5V) into Output (-10V - +10V)

Thread Starter

1sagain2

Joined Jan 23, 2019
5
Hello!

I need to create a circuit with variable input form 0V to +2.5V. The Output should be from -10V to +10V
So 0V input should provide a -10V output; a 2.5V input should provide a +10V output.

Does someone have an idea how the circuit could look like? Preferably with analog electronics.
I thought about a circuit with an OP-Amp, but can't figure out how to reach the negative voltage.

Thanks!
 

ericgibbs

Joined Jan 29, 2010
12,270
hi,
Don't forget to add some decoupling caps on the power rails.
You could make R1 a variable, say 4k7 fixed and a 5k trim pot in series.
E
 

Thread Starter

1sagain2

Joined Jan 23, 2019
5
Question to your idea: What do you need The first OpAmp for? Why don't you just put 1.25V directly to R2?
Because the Output of the first OpAmp is always 1.25V..
 

ericgibbs

Joined Jan 29, 2010
12,270
hi,
Its not always possible to guarantee the 'stability' of the main +12V, so I use a Zener source.
The first OPA has a low output impedance, as you know R1 and (R2+OPA1 Zout) set the gain of the second OPA.
So I always prefer to use a OPA source for the input to the second OPA.
If you want to economise on components, you could omit the 1st OPA, but as you vary the Vref setting, the gain of the second stage will change, so then you have to adjust R1 to get the correct gain,,, and so on until its set up.
E
EDIT:
Added datasheet for OPA, an equivalent specification will be OK.
 

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Thread Starter

1sagain2

Joined Jan 23, 2019
5
Hi E,
that is very clever! You thought way ahead of what i thought about. Thank again!

No need for meto economise on components, so i will defintely use the 1st OPA.
 
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