Question
I want to know:
1. What is the Open-loop gain of the AD8532?
2. Where the low frequency/ dominant pole(s) locates in hertz?
3. where high frequency pole / second pole(s) locates in hertz? in Figure 15 in
datasheet Rev F this seems to be at 10 MHz, is this right?
Answer
We do not have more data than shown in the datasheet. AD8532 has Unity-Gain
Bandwidth of 3MHz and the phase margin appears to be around 65deg. Gain goes up
20dB per decade, so at
3MHz, it is 0dB
300K,it is 20dB,
30K, it is 40dB
3K, it is 60dB
300, it is 80dB
30Hz, it is 100dB
Until it reaches the dominant pole where it flattens. We know that for every
pole, we get 90 degree of phase shift. The fact that the spec table shows 98dB
as the large signal gain at DC, I would think that the dominant pole is between
30 and 300Hz. Non-dominant pole as read from the graph appears to be around
10MHz. These are estimates and designers usually do not give this info out
since there are many poles and zeros that are in play and we are approximating.