Will an open loop op amp with negative phase margin oscillate?

I understand phase margin is defined in closed loop transfer function with equating denominator to zero . But will an insufficient phase margin show signs for open loop connected op amp?

  • \$\begingroup\$ Beware of parasitic components such as stray capacitance, that may accidentally provide feedback, unintentionally closing the loop. \$\endgroup\$ Feb 27 '16 at 10:30
  • \$\begingroup\$ How would you use an opamp without negative feedback? You get a comparator like circuit, well if you put the feedback then the phase margin comes to play. \$\endgroup\$ Feb 27 '16 at 12:48
  • \$\begingroup\$ For example a LNA which shall be belonged to the class of op amp. Ignoring unwanted parasitic feedback, I think the amp is intended to be used in open loop. \$\endgroup\$
    – Eagle Shou
    Feb 28 '16 at 20:41
  • \$\begingroup\$ LNAs in RF front ends tend to have finite, defined and quite low gain (10dB to 20dB). They are generally not opamps. \$\endgroup\$ Mar 1 '16 at 22:31

No, an open loop system will not oscillate. Comparators are a good example for this.

The phase margin is determined for the open loop system but is relevant for the closed system only.


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