Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

enter image description here

In the book first this form of half-wave rectifier voltmeter is introduced and then the author says that there is a problem in this circuit that when the ac source is in the reverse direction there is a chance that the diode may break-down causing damage to meter , I understand this part , then he gives a modified version of this voltmeter .

enter image description here

Now he says that during reverse operation this D2 will be forward biased and there will be no problem .

But now there is a problem when the AC is positive , I mean this diode D2 can break-down in the postive operation . Nothing has been mentioned about this . I simply wanted to confirm , am i right in thinking so ? And If I am not what may be the reasons .

share|improve this question
it sounds reasonable what you say. – Andy aka Feb 15 '14 at 20:20
If Rm is very much less than Rs, the reverse voltage across D2 will be low. – Brian Drummond Feb 15 '14 at 20:31

There is never more than a single diode voltage drop across either diode (disregarding the small voltage across the meter itself for sake of the discussion). In this configuration he diodes will not break down due to reverse overvoltage as for each half period one diode will be conducting.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.