| ??? 12/24/06 03:53 Modified: 12/24/06 04:08 Read: times |
#130056 - ??? Responding to: ???'s previous message |
Alireza said:
but as I said in first post providing alternative feedback path as suggested by you ... has some drawbacks Phase lead does not use an alternative feedback path, but the existing from load to diff amp. Alizea said:
and the most important is reduction of sensitivity of error amp especially at higher frequencies, so error amp can't control output voltage precisely. Sorry?? Just the opposite is right: Phase lag slows down the amplifier, but adding phase lead speeds it up, optimizes the bandwidth, maximizes the loop stability and minimizes the settling time. Read the chapter "OPamp settling time - a mathematical model" of this datasheet: http://www.analog.com/UploadedF.../AD711.pdf Alireza said:
but amount of this feedback should be very limited and other parts of this loop should be optimized so we can have both stability and precision. Yes, that's what phase lead does. Alireza said:
The question is how, I have read in brochure of some laboratory instruments that they have introduced loop stability factors that I guess are used to deal with this problem. As much as I could find information about them, they are used to limit bandwidth of power amp, I don't know how, and exactly what they are. What answer do you expect, when your given details are such meager?? What power amp, what diff amp, what error amp, what load, what sine, what bandwidth, what laboratory instruments, what brochure, what application??? Kai |
