OP-AMP Circuits

What exactly is an OPerational AMPlifier?
Let's define what that component is and look at the parameters of this amazing device. An operational amplifier IC is a solid-state integrated circuit that uses external feedback to control its functions. It is one of the most versatile devices in all of electronics. The term 'op-amp' was originally used to describe a chain of high performance dc amplifiers that was used as a basis for the analog type computers of long ago.

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The very high gain op-amp IC's our days uses external feedback networks to control responses. The op-amp without any external devices is called 'open-loop' mode, referring actually to the so-called 'ideal' operational amplifier with infinite open-loop gain, input resistance, bandwidth and a zero output resistance. However, in practice no op-amp can meet these ideal characteristics. And as you will see, a little later on, there is no such thing as an ideal op-amp. Since the LM741/NE741/uA741 Op-Amps are the most popular one, this tutorial is direct associated with this particular type. Nowadays the 741 is a frequency compensated device and although still widely used, the Bi-polar types are low-noise and replacing the old-style op-amps.
Shown in Fig.1 at the right are op-amp symbols as usedtoday. The one on the right is an older way of drawing it but still used in books like the ARRL (American Radio Relay Leaque) and older schematics. It is common practice to omit the power supply connections as they are implied.

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