Integrated Circuits and Systems group, IIT Madras

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courses:el3203_2014:phasemargin [2014/01/27 05:18] (current)
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 +====== Amplifier phase margin ======
 +  * Goals:
 +    * Understand the effects of extra phase shifts in a feedback loop
 +    * Learn a technique to squeeze out more bandwidth in a feedback amplifier
 +
 +{{:​courses:​ec330_2008:​invamp1.png?​500}}
 +
 +  * Design the amplifier in (a) for a gain of -10. What is the expected 3dB bandwidth? Measure the bandwidth by sweeping the input sinewave frequency. Is there peaking(gain at some frequency higher than the dc gain) in the frequency response? What is the bandwidth? Measure the step response by applying a low frequency square wave. Is there an overshoot? ​
 +
 +  * What happens when there is a capacitance from the inverting terminal of the opamp to ground? Connect larger and larger capacitors(starting from 100pF or less) and see what happens to the step response and the frequency response. Explain.
 +
 +  * Adjust C<​sub>​p</​sub>​ to get the largest bandwidth possible with no peaking in the frequency response. How does this bandwidth compare to the previous case? Explain clearly. Measure the step response and its overshoot, if any.