An operational amplifier is an integrated circuit normally housed inside an 8 pin duel inline package. The characteristics of the device (i.e the voltage gain input, output impedance), are considerably better than transistor devices. It can be used for a number of amplifying purposes depending on the connection of the external components.

Fig.1 shows the Op-Amp symbol with pin allocation.

fig.1

As a single device the op-amp passes very high gain, typically 20,000. To restrict this gain a resister is wired between the output and inverting terminal of the op-amp. This provides what is called negative feedback that yields the following op-amp characteristics:

1. High input resistance (100K to 10M ohms)
2. Low output resistance (50 to 100 ohms)
3. Wide frequency response

The 741 device requires a split supply.

Pin 7 +3V to +15V
Pin 4 -3V to -15V
Pin 2: inverting input (-)
Pin 3: non-inverting input (+)

A signal applied to pin 2 experiences an inversion at the output whilst a signal applied to pin 3 experiences no inversion. The op-amp is therefore also able to amplify the difference between the two signals applied to its input.