General Purpose op-amp can serve the role of instrumentation amplifier which costs than general-pupose op-amp but there is more to it.
To add to previous guys is that instrumentation amplifier has features other guys mentioned especially CMRR value which distinguish it from other op-amps. Plus it has high input impedance.
Instrumentation amplifier is a differential voltage op-amp loosely said while this can be contructed with 741's for example but is easy to build the thing as one chip rather than having two,three,four opamps in circuitry.
One more thing: if you create a differential voltage circuit using 741 opamp what would be its input impedance? Think about it. Visualize the schematic. Add resistors, do you really have high input impedance?
Sherif zakaria saw your report, it is good tutorial (a detailed report) for everyone who wants to learn for instrumentation op-amps in microelectronics. I recommend it to initiator of this thread to read it.
Good work!
Generally speaking, you can use three identical ordinary Op-Amp to construct a so called instrument Op-Amp in order to obtain better CMRR resulting from its symmetry structucture.
An instrumentation amplifier is a type of operational amplifier that has been specifically designed to have characteristics suitable for use in measurement and test equipment. These characteristics include very low d.c. offset, low drift, low noise, very high open loop gain, very high common mode rejection, and very high input impedances. They are used where great accuracy and stability of a circuit both short and long term are required.