[SOLVED] Adding offset to amp

[dawid5255252]

Hello,
I would like to make voltage regulator using op-amp. I want to give 0-10V on input and get -5V to 5V on output.
I made inverting amplifier with ku=-1. My problem is that I need to add offset 5V to amp, but I don't know how to do it.
Schematic is below:

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I know, that I need to use input "1" and "5" and I tried simply to give 5V to them, but it didn't change anything.
Please give me advice!

 

[chuckey]

Take the + input to the centre of two equal resistors strung between the +10V and 0V lines.
Frank

 

[dawid5255252]

The problem isn't making 5V voltage. The problem is how to connect this offset to op-amp inputs to work fine.
Look on picture below:

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I want to make regulation:
IN:10V --> OUT: -10+5=-5
IN: 5V --> OUT: -5+5=0
IN:0V --> OUT: 0+5=5

I connected 5V to input "1" and "5". I giving on input 10V and I getting -10V at output. And I would like to get -5V on output when input is 10V. I can't get/connect offset.

 

[Audioguru]

The input voltages of a linear opamp are almost the same because its open-loop voltage gain is very high. The (+) input voltage is 0v so the (-) input is also 0V.
1) You want the output to be -5V when the input is 0V so R2 has 5mA in it.
2) You want an offset resistor to also have 5mA in it from the opposite polarity so a 2k resistor to +10V will DOO DAT.

Check the output voltage when the input is -5V and when it is -10V. Use Ohm's Law to check it.

- - - Updated - - -

You DID NOT do what Chuckey told you to do.
Pin 1 and pin 5 ARE NEVER connected together and they are not the (+) input which is pin 3.
You have a resistor to the input instead of to +10V like Chuckey said.
Can't you read?

 

[LvW]

Dawid, what Audioguru has proposed is nothing else than to use the opamp as an adder (inverting).
Add a voltage of -5V to the output signal - and everything works as desired.
For this purpose, you can use +10V (as shown by Audioguru via a 2k resistor) or +5V (via 1k resistor).

 

[FvM]

I think only chuckeys suggestion achieves the intended level shift. The offset voltage at the + input should be however 2.5 instead of 5 V, requiring a 3R:R voltage divider.

There's a certain contradiction-in-terms in the original post, "give 0-10V on input and get -5V to 5V on output" would refer to non-inverting amplifier at first sight. Should be changed to "get +5V to -5V" for clarity.

 

[dawid5255252]

Works very well!
Thank you for solution!

 

[Audioguru]

Which one works very well?

 

[JAMAL JIMI]

Dear.......You can use a 500ohms potentiometer with two 4.7k resistors.......this will provide you a fine adjustment for offset.