buddypoor wrote on Apr 30th, 2012, 3:13am:@ricky: Sorry, I didn't see the phase (forgot to scroll). Please, can you confirm that you have used the "double-injection technique" ? (Because the term "Middlebrook" is somewhat ambigious).
@raja: In most cases (in particular for opamps without transfer function zeros and with a continuous gain decrease) the phase response is directly related to the gain response and, thus, must not be shown explicitely. In these cases, the phase margin can be estimated using the SLOPE of the gain function only. In particular, if the 2nd pole is approx. at the unity gain frequency (slope changes from -20 to -40 dB/dec) the PM will be approx. 40...50 deg.
1:- Middle-Brook theorem is NOT ambiguous at all.
2:- Yes it is 'double injection technique' i.e. I found RRi(injecting current) and RRv( injecting voltage) at the break point.
This is clear from the schematic I have shown.
3:- From gain plot it is very difficult to figure the PHASE AMrgin.
As it may have pole zero pairs.