Page 1116 - Basic Electrical Engineering

Figure 17.3 Pin diagrams of IC op-amp 741. (a) 8-pin mini dip packaging; (b) 8-pin metal can
packaging

The circuit symbol of an op-amp has been shown in Fig. 17.4. The input

terminals are marked a and b. Terminal a is marked negative while terminal b
is marked positive. Terminal a is the inverting terminal. The input provided at

this terminal appears inverted at the output with amplification. Terminal b is
non-inverting. The output for input at b appears non-inverted but amplified.

When signals are provided at both a and b terminals, the output at terminal c
is proportional to the difference of the two signals.

The internal circuit is quite elaborate. But the user of an op-amp need not
go to the details of the functioning of the op-amp circuit. The user has to
know the basic specifications and the terminals so as to make connections

with external circuit components for a purpose.
The power supply voltages which are usually balanced with respect to the

ground are applied to terminals 7 and 4, i.e., to terminal d and e as in Fig.
17.4 Terminals d and e are often not shown in the circuit diagrams using op-
amps.

An ideal op-amp has the following characteristics:

i. Infinite input impedance
ii. Zero output impedance
iii. Infinite voltage gain
iv. Infinite bandwidth
v. Perfect balance (i.e., output is zero when both the inputs are equal)