normad
Member
Im trying to understand the gain change in a buffer amplifier with a low frequency gain of 1.
I simulated the op-amp on ltspice and according to that the gain does not change with frequency but the phase does..
(i uploaded the ltspice file.. i changed the opamps gbw to 5Meg as we are supposed to do this lab with lf347s)
what i dont understand is..
if there is a phase difference between the input and the output that means the feedback will also have a phase difference.. if there is a phase difference in the feedback shouldnt the difference be amplified? so the gain should either decrease or increase as frequency reaches GBW.. but in the simulation it remains the same..
and when we did this experiment in the lab the gain slightly increased with frequency..
i derived an equation for the gain considering the op-amps input impedance as Rin and the opamp gain as AvΓθ where is the phase difference
and what i got is
Vo Rin*AvΓθ
------ = --------------------------------
Vin (Rin+1) + (2Rin+1)*AvΓθ
doesnt this mean gain depends on phase difference?
please help.. thanks![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I simulated the op-amp on ltspice and according to that the gain does not change with frequency but the phase does..
(i uploaded the ltspice file.. i changed the opamps gbw to 5Meg as we are supposed to do this lab with lf347s)
what i dont understand is..
if there is a phase difference between the input and the output that means the feedback will also have a phase difference.. if there is a phase difference in the feedback shouldnt the difference be amplified? so the gain should either decrease or increase as frequency reaches GBW.. but in the simulation it remains the same..
and when we did this experiment in the lab the gain slightly increased with frequency..
i derived an equation for the gain considering the op-amps input impedance as Rin and the opamp gain as AvΓθ where is the phase difference
and what i got is
Vo Rin*AvΓθ
------ = --------------------------------
Vin (Rin+1) + (2Rin+1)*AvΓθ
doesnt this mean gain depends on phase difference?
please help.. thanks