# Operational Amplifier (Op-Amp)

An operational amplifier is a direct- coupled high gain, differential-input amplifier.

With the addition of suitable external feedback components, an op-amp can be used for a variety of application, such as ac and dc signal amplification, active filters, oscillators, comparators, regulators, and others.

# Operational Amplifier Terminals

**Operational amplifier**

Op-amp has five basic terminalsâ€”

- Two for input signals,
*V*_{1}and*V*_{2}â€“ differential input terminals. - One for output signal,
*V*_{0}single-ended output. - Two for power supply, +
*V*and â€“*V*. (Maximum*V*= Â± 18 V)

# Op-Amp Characteristics

*Ideal Characteristics*- An infinite voltage gain
- An infinite bandwidth
- An infinite input impedance
- Zero output impedance
- Perfect balance, i.e., the output is zero when equal voltages are present at the two input terminals; and
- The characteristics do not change with temperature

*Practical (Actual) Characteristics*- The gain at low- frequency is finite and very high (of the order of 10
^{3}to 10^{6}). The gain is constant upto a few hundred kHz_{ }and then decreases monotonically with the increase in frequency. - The bandwidth is finite and very high.
- The input impedance lies in the range of 150 kÎ© to a few hundred M
- The output impedance of a practical op-amp lies between 0.75 to 100 Î©.
- Perfect balance is not achieved with practical op-amps.