Hey guys, ok i have been pondering this for ages, and cant understand it:
In my notes, the phase relation of output to input is given by: theta = atan(f/fc) where fc is the frequency corresponding to Aol = 1/b
So finding the phase angle at any frequency f is done by the above formula.
But why is this so? Why must the frequency be calculated with respect to fc? What does having the circuit in a closed loop have to do with the phase of the output?
I have another nagging annoyance as well:
The performance of an opamp can be represented by the following equation:
Actual performance equation = ideal performance * 1/(1+(1/BAol(jf)))
What is the performance then when Baol is = 1? The reason why i dont understand this is because to eliminate the j in the equation, my lecturer found the modulus of the complex number only (which i also dont understand why this can be done)
For example: gain error was found for some circuit to be: 1/(1+0.1J)
to eliminate the j, lecturer got the modulus of the denominator like: sqrt(1^2 - 0.1^2)
How and why can this be done? And following this line of thought, at BAol = 1, wont the gain error be: 1/(1-1) which is infinity?
If j is in the equation, then its a complex number and a real number divided by a complex number is a complex number! How can just finding the modulus of the comlex number be used here?
Thanks!
In my notes, the phase relation of output to input is given by: theta = atan(f/fc) where fc is the frequency corresponding to Aol = 1/b
So finding the phase angle at any frequency f is done by the above formula.
But why is this so? Why must the frequency be calculated with respect to fc? What does having the circuit in a closed loop have to do with the phase of the output?
I have another nagging annoyance as well:
The performance of an opamp can be represented by the following equation:
Actual performance equation = ideal performance * 1/(1+(1/BAol(jf)))
What is the performance then when Baol is = 1? The reason why i dont understand this is because to eliminate the j in the equation, my lecturer found the modulus of the complex number only (which i also dont understand why this can be done)
For example: gain error was found for some circuit to be: 1/(1+0.1J)
to eliminate the j, lecturer got the modulus of the denominator like: sqrt(1^2 - 0.1^2)
How and why can this be done? And following this line of thought, at BAol = 1, wont the gain error be: 1/(1-1) which is infinity?
If j is in the equation, then its a complex number and a real number divided by a complex number is a complex number! How can just finding the modulus of the comlex number be used here?
Thanks!