Two silicon diodes, with a forward voltage drop of 0.7 V, are use

Two silicon diodes, with a forward voltage drop of 0.7 V, are use
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Two silicon diodes, with a forward voltage drop of 0.7 V, are used in the circuit shown in the figure. The range of input voltage 𝑉𝑖 for which the output voltage 𝑉𝑜 = 𝑉𝑖, is

A. &minus;0.3 𝑉 &lt; 𝑉<sub style="">𝑖</sub> &lt; 1.3 𝑉

B. -0.3 V &lt; V<sub style="">i</sub> &lt; 2 V

C. -1.0 V &lt; V<sub style="">i</sub> &lt; 2.0 V

D. -1.7 V &lt; V<sub style="">i</sub> &lt; 2.7 V

Please scroll down to see the correct answer and solution guide.

Right Answer is: D

SOLUTION

Try to solve all the diode related questions with the following approach:

1) Consider all the diodes to be off.

2) Now, first, calculate the voltage across each diode.

3) If the diodes have greater voltage than cut-in voltage, consider that the diode to be on which has higher voltage.

4) Now, again calculate the voltage across the remaining diode by considering that particular diode to be ON.

5) Again check which diode has a greater voltage considering it ON, and the process continues till we get to know the state of each diode.

Analysis:

Given: Vr = 0.7 V

When Vi > 2.7 V, the output voltage will be fixed to:

V0 = 2.7 V

When Vi < -1.7 V, the output voltage will again be fixed to:

V0 = -1.7 V

When -1.7 V < Vi < 2.7 V, both the diodes are OFF and:

V0 = Vi

∴ The transfer characteristics can be drawn as:

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