Characteristics of Ideal and Practical Operational Amplifiers:

An Ideal op-amp is basically a differential voltage-controlled-voltage-source (VCVS) possessing infinite gain, infinite input impedance and zero output impedance. A variety of IC op-amps, similar to such ideal behavior, are commercially available now out of which, the internally-compensated types such as µA741 and LF356 are comparatively more popular.

An operational amplifier is basically a very high gain differential amplifier with the following ideal properties

Figure: Ideal Op-amp Symbol, Equivalent Circuit and Pin Configuration of µA741 IC Ip-amp

- infinite voltage gain               (i.e. A → 00)

- infinite input impedance         (i.e. input terminals draw zero currents when connected so source)

- zero output impedance          (i.e. it acts as an ideal voltage source w.r.t output terminal)

- infinite bandwidth                  (i.e. gain remains constant from zero frequency to infinity)

- zero offset voltage                (i.e. V₀  = 0 when V₁ = 0 = V₂

- zero drift                              (i.e. parameters not changing with temperature)

An ideal op-amp may be regarded as a differential input Voltage-Controlled-voltage- source (VCVS), as illustrated in Figure. A large variety of IC op-amps are available out of which the internally compensated types like 747, µA741,LM324, LF356 have been the more popular ones. The pin configuration for 741 type op-amp is given in above Figure (b), and its important parameters are given in Table

Table: Typical Parameters Values of a 741-type Op-amp