The 741 operational amplifier is one of those chips you will probably encounter in college or high school technology and electronics classes.
It has been around almost as long as integrated circuits.
The name 'operational amplifier' comes from the fact that the amplifier was used in early analogue computers to perform 'operations' such as adding and subtracting analogue values.
The text below explains the packaging of a 741 operational amplifier chip in the classic eight pin DIL chip package, and the table shows the pinouts.
DIL = 'Dual in line'.
Two rows of four pins sprout from each of two opposite and parallel sides of the body.
There is a very obvious notch, easy to find with a fingernail, on the top of one of the sides with no legs. If you hold the chip with this notch at the top, away from you, pin 1 is to the left of this notch, and the pins are numbered in an anti-clockwise direction round the chip. So pin 1 is at the top left, pin 4 at bottom left, pin 5 at bottom right, and pin 8 at top right.
I have seen some DIL chips with a very small recessed dot instead of the obvious notch, next to pin 1. If you cannot find the notch, feel around with a sharp non-conductive object and see if you can find this tiny recessed dot.
This table shows the function of each pin:
|2||Inverting input terminal|
|3||Non-inverting input terminal|
|4||-Vcc (negative voltage supply)|
|7||+Vcc (positive voltage supply)|
The main pins in the 741 op-amp are pin2, pin3 and pin6. In inverting amplifier, a positive voltage is applied to pin2 of the op-amp; we get output as negative voltage through pin 6. The polarity has been inverted. In a non-inverting amplifier, a positive voltage is applied to pin3 of the op-amp; we get output as positive voltage through pin 6. Polarity remains the same in non-inverting amplifier. Vcc is usually in the range from 12 to 15 volts. When two supplies (+Vcc/-Vcc) are used, they are the same voltage and of opposite sign in almost all cases. Remember that the operational amplifier is a high gain, differential voltage amplifier. For a 741 operational amplifier, the gain is at least 100,000 and can be more than a million (1,000,000). That's an important fact you'll need to remember as you put the 741 into a circuit.
There are many common application circuits using the 741 op-amp, they are adder, comparator, subtractor, integrator, differentiator and voltage follower.