Voltage follower Unity Gain Bandwidth

[student_of_analog]

Hello,

I read somewhere that Bandwidth of a voltage follower is maximum.
Can anybody help me understand why this is ?

 

[jimito13]

I read somewhere that Bandwidth of a voltage follower is maximum.

This is a very general statement...for an ideal voltage buffer it is infinite,for a real one it is finite.
It depends on how much "finite" you want for your application.
That's all.

 

[student_of_analog]

Thanks but I wanted to know from an equation point of view.
If the open loop DC gain is 100 dB and UGB is 25MHz and I connect this opamp in Unity Gain loop (voltage follower).
Then what is the bandwidth of this topology(voltage follower) compared with other closed loop topologies (for ex. with closed loop gain of 10).

 

[jimito13]

Check chapter 9.2 of Gray-Meyer.

 

[student_of_analog]

Thanks you . I looked at it. The chapter talks about gain bandwidth in closed loop.
Actually I was trying to understand the difference between gain bandwidth in closed loop and in open loop.
Can you tell me how they are different. I understand that Gain * Bandwidth should remain constant.
So, are Gain (open loop) * Bandwidth (openloop) = Gain (closed loop) * Bandwidth (closed loop) ?