operational amplifiers(opamp 741)

[patilsuchita]

why opamp has infinite input impedance, infinite bandwidth, infinite slew rate, infinite CMRR, Zero output impedance, infinite voltage gain.

please its urgent.

suchita

 

[chippevijaya]

That's ideal condition, Op-amp 741 has input resistance of 0.3M Ohms max. Bandwidth of 1.5 MHz only, and slew rate of 0.5.
You find still more high resistance, bandwidth, slew rate and ver low output impedance in still different op-amps.
The ideal conditions are defined to measure op-amp's max conditions, but in practical these are very for every op-amps

 

[LvW]

why opamp has infinite input impedance, infinite bandwidth, infinite slew rate, infinite CMRR, Zero output impedance, infinite voltage gain.
please its urgent.
suchita

As mentioned in post#2, you have listed IDEAL conditions that never can be met.
However, to answer your questions:
All opamp manufacturers try to approach an ideal VOLTAGE amplifier.
Such an amplifier must draw no current (high input resistance) and must be able to deliver the amplified signal as a voltage source (low output resistance).
It is clear that this function should be provided over a frequency span that is as large as possible (bandwidth).
The infinite gain Aol (open-loop gain) helps to make the overall gain due to the feedback circuit nearly independent on the actual value of Aol.
That means the overall gain is determined by the feedback resistors only.
Hope it´s clear now.

 

[garyson02]

Opamp having differential amplifier in it. also it will draw less input signal

BW is 10 Hz(openloop)
BW is 1MHz(closedloop)

 

[patilsuchita]

oprational amplifiers(opamp 741)

why opamp has high voltage gain, infinite common mode rejection ratio, infinite slew rate

please describe or give any link or material to study?


urgent


suchita

 

[FvM]

No real OP has infinite CMRR or SR. It has high (open loop) voltage gain by design, according to it's working principle.

https://en.wikipedia.org/wiki/Operational_amplifier

 

[rock94]

They are the ideal conditions(theoritical). However in during application the values are never equal to the ideal value although they come very close to it.

 

[crutschow]

Those are the ideal values since that means the op amp contributes no errors or frequency limitation to the circuit, it would be perfect. Real devices do, of course, have limitations on all those characteristics.

 

[schmitt trigger]

"Real devices do, of course, have limitations on all those characteristics."

Specifically a 741 opamp. This was designed over 40 years ago, and although state of the art back then, nowadays it has many limitations compared to newer devices.