In the circuit shown below, the voltage appearing across the diode D will be of the form : [figure]
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Answer
(4) [figure]
Solution
The cathode (bar) of D is towards the upper terminal of the source and its anode is towards R.
Positive half cycle: upper terminal at higher potential ⇒ D is reverse biased (open circuit) ⇒ no current, so the whole input appears across D: vD = vi
Negative half cycle: D is forward biased (ideal, short circuit) ⇒ vD = 0 and the input appears across R.
vD shows the positive half cycle followed by zero in the negative half cycle.
Answer: (4)