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AD8513 Wide Bandwidth and Phase Reversal

Question asked by AngelicaZ on Dec 20, 2017
Latest reply on Jan 8, 2018 by ARoxas


I am analyzing stability of a number of circuits using AD8513, my first approach is through PSpice simulation and rate-of-closure criteria. So first, I need to confirm the model of this opamp behaves as it is depicted in its datasheet. In Figure 17 "Open-Loop Gain and Phase vs. Frequency", the X-axis starts at 10kHz and ends up to 50MHz. I ran an AC Sweep simulation to replicate Figure 17 (open loop, RL=2.5k and Cscope=20pF):

From comparing the right hand plot versus the left hand plot, one could assume that the model behaves as it is expected from the datasheet:


The question rises when the X-axis of the same plot above is zoomed out to start at 1Hz in the PSpice simulation; the phase is reversed 180° at low frequencies (lower than ~61Hz). Is the model of the opamp inaccurate? or I should expect such behavior at low frequencies?:

Thanks a lot for your support and your time!