Op-amp Symbol and Terminals

Op-amp Symbol and Terminals

The symbol for an op-amp along with its various terminals, is shown in the Fig. 2.2.1.

The op-amp is indicated basically by a triangle which points in the direction of the signal flow.

All the op-amps have atleast following five terminals :

i) The positive supply voltage terminal V_CC or + V.

ii) The negative supply voltage terminal - V_EE or - V.

iii) The output terminal.

iv) The inverting input terminal, marked as negative.

v) The noninverting input terminal, marked as positive. 

The input at inverting input terminal results in opposite polarity (antiphase) output. While the input at noninverting input terminal results in the same polarity (phase) output. This is shown in the Fig. 2.2.2 (a) and (b). The input and output are in antiphase means having 180° phase difference in between them while inphase input and output means having 0° phase difference in between them.

The op-amp is fabricated on a tiny silicon chip and packaged in a suitable case. Fine gauge wires are used to connect the chip to the external leads.

The op-amp works on a dual supply. A dual supply consists of two supply voltages both d.c., whose middle point is generally the ground terminal.

The dual supply is generally balanced i.e. the voltages of the positive supply +Vcc and that of the negative supply - VEE are same in magnitude. The typical commercially used power supply voltages are ± 15 V. But if the two voltage magnitudes are not same in a dual supply it is called as unbalanced dual supply. The balanced and unbalanced types of dual supply are shown in the Fig. 2.2.3 (a) and (b) respectively.

Practically in most of the op-amp circuits balanced dual supply is used. The other popular balanced dual supply voltages are ± 9 V, ± 12 V, ± 22 V etc.

Review Question

1. Draw the op-amp symbol and explain the various op-amp terminals.