Dual power supply for Op Amp

amplifierarduinodcicl7660power supply

We have dual power supply units (+- 12V DC with common GND) at our college lab using which I am able to implement my project (digital thermometer) which uses op amps as shown in the figure.

I'm using an LM35, three op amps, an Arduino Uno, and an LCD display.
I need to make this a product which can be run using only one external power supply (+12V DC adapter for the Arduino).

I tried using a voltage divider circuit to supply +6V and -6V DC to the op amps. However, when I connect the LM35, feedback resistors and other components, the voltages measured at various stages are not as expected.
In fact, the input voltage itself changes it's value from +6V to +2V and the other voltage changes to -10V from -6V.
One thing I have noticed is that there is a constant voltage difference of 12V between the input pins.

Why am I getting weird values of voltages?
Is this called the "loading effect"?
What are the other possible ways of supplying power to the op amps using the 12V adapter?

The schematic that works with the dual power supply unit at my college

EDIT: This is the schematic that works with the dual power supply unit (+-12V) at my college. I want to make this device portable. Hence, I can't use the dual power supply all the time. Need a solution for this…

Best Answer

  1. The µA741 can be used in single voltage applications.
  2. The 741 is pretty lousy as far as op-amps go.
  3. There are better op-amps that work better on single voltage supplies.
  4. You cannot power an op-amp from a voltage divider (insane things like two 1 Ohm resistors excluded.)

What you need to do is to look up single voltage operation for op-amps, and see what you need to do. Hint: It does involve a voltage divider, but not powering the amp.

Here is an example of a 741 running on a single voltage: enter image description here

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