Picture of Non-inverting amplifier with uA741
The Operational Amplifier is probably the most versatile Integrated Circuit available.  The most common Op-Amp is the 741 and it is used in many circuits, as it is very cheap. Its main purpose is to amplify (increase) a weak signal.

The OP-AMP has two inputs, INVERTING ( - ) and NON-INVERTING (+), and one output at pin 6. The chip can be used in a circuit in two ways. If the voltage goes into pin 2 then it is known as an INVERTING AMPLIFIER (it reverses the polarity of the input signal).
If the voltage goes into pin 3 then the circuit becomes a NON-INVERTING AMPLIFIER, the onj that we are going to build now.

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Step 1: Theory of operation and Simulation

Picture of Theory of operation and Simulation
As you may see from the schematic, only a few components are needed to build the circuit.
The circuits accepts as input a small signal, and gives the amplified signal (with same frequency and same polarity of the original) at the output. The gain is controlled by the two resistors R1 and R2, by this simple law:

GAIN (AV) = 1+(R2 / R1)

Example : if R2 is 1000 kilo-ohm and R1 is 100 kilo-ohm the gain would be :
GAIN (AV) = 1+ (1000/100) = 1 + 10 = 11
So if the input voltage is 0.5v the output voltage would be :
0.5 X 11 = 5.5v

Note that you may not amplify the input signal as you want: the output signal is limited by the two IC's power sources: in this case the output signal cannot be greater than +12V.
Also note that the output signal may be altered even if the input signal's frequency and amplitude is too high (try searching for "Slew Rate").

Step 2: UA741 on a breadboard

To build this circuit you'll need:
1x    1.2KOhm resistor
1x    47KOhm resistor
1x    UA741CD  OpAmp
1x    Function Generator
1x    Oscilloscope (even a multimeter would be fine, but you cannot see the waveform)
1x    +- 12V Power Source
1x   Breadboard (even a small one)

After you assembled the circuit as in the picture, we are ready to see the results of our amplifier!

shiv2131 year ago
Can this arrangement be used to amplify sound if we have a speaker at the output and a mic input somewhere?

Yes, however you should have your mic input hooked up to the 3pin and your speaker on the 6pin, like in the schematic. It should amplify the AC current from the microphone.