voltage gain and bandwidth of an op-amp

[rajasekharnbkrist]

Hi,all

In op-amp the band and openloop voltage gains are equal to infinity, what is the advantage of keeping both infinity

 

[Audioguru]

The voltage gain and bandwidth in opamps ARE NOT INFINITY!

The open-loop (no negative feedback) voltage gain for most opamps is about 200,000 at DC and very low frequencies up to about 10Hz.
The frequency compensation capacitor in an opamp reduces its gain 6db per octave (20dB per decade) so that at a frequency where phase shifts in the opamp would cause oscillation when negative feedback is applied, the gain is less than 1 so the opamp does not oscillate.

Some good audio opamps (OPA134) have an open-loop gain of 1 million at DC and very low frequencies. Its gain is 1 at 8MHz.

 

[LvW]

Hi,all
In op-amp the band and openloop voltage gains are equal to infinity, what is the advantage of keeping both infinity

In some basic operations the frequency-dependence of the opamp gain is neglected and corresponding rough calculations are performed based on the assumption that gain and bandwidth are infinite.
Thus, calculations are drastically simplified and the corresponding errors are within acceptable limits.

 

[rajasekharnbkrist]

What is the meaning of virtual ground concept , what is the advantage of keeping virtual ground

- - - Updated - - -

i want what is the advantage of having infinity bandwidth for an ideal op-amp

 

[LvW]

What is the meaning of virtual ground concept , what is the advantage of keeping virtual ground

The virtual ground concept allows us to set Vp=Vn=0 for inverting opamp applications. This assumption drastically simplifies all calculations.

i want what is the advantage of having infinity bandwidth for an ideal op-amp

In this case, we can simply neglect (forget) the frequency-dependent properties of the real opamp.
However, one must be aware that such an approach is not always allowed - and it is a typical enginneering task to decide in which case such an approach is appropriate.