# a 741 simple circuit diagram

#### eliza

Joined Feb 11, 2008
1
hi,
I need a simple circuit diagram for 741 op-amp,I also need to know how to have a negative voltage ?
thx

#### Papabravo

Joined Feb 24, 2006
13,923
Look in the data sheet for application examples. Choose a more modern part than the 741 it was obsolete 30 years ago. A negative supply is derived from a transformer with a grounded center tap.

#### SgtWookie

Joined Jul 17, 2007
22,210
Have a look at the attached circuits. Note the connection of two 9V batteries to obtain + and - supply voltages around ground.

They're both configured as non-inverting amplifiers; the first one has it's gain fixed at 2:1; IE: for given input voltage, it's output is double.

The 2nd one is variable from 1:1 to 100.1:1.

If you look at the output from a "real" 741, you will see a phenomenon known as "phase reversal", "phase inversion" and "lockup" when the gain times input exceeds the capability of the device. Modern op amps have internal circuitry which prevent this.

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#### Audioguru

Joined Dec 20, 2007
11,249
If you bias the inputs properly and use coupling capacitors then an opamp does not need a negative supply.

#### SgtWookie

Joined Jul 17, 2007
22,210
Audioguru,
While I agree with you as far as AC signals go, that would not help the OP if they were looking at DC levels. I had to assume that:
1) The OP is very new to op amps
2) The circuit needed to be capable of handling anything from a DC level to the op amp's BW limitations (which in the case of the 741 is rather severe, but it's still a good exercise for a beginner. )
3) The OP needed an example of how to create a negative voltage level.

I could have shown the use of a resistive divider across a single 9v battery, but considering the OP's requirement of a 741 demonstration, that wouldn't have left much useable headroom.

Were the 741 an automobile, it would be a rusty 1966 Ford Fairlane with a small straight 6-cylinder engine, manual shift and patched seat covers.

It makes one appreciate the Jaguars and Ferraris available nowadays so much more