Two silicon diodes with a forward voltage drop of 0.7 V, are used in the circuit shown below. The range of input voltage V_i for which the output voltage V_o = V_i is :

Concept:

Two silicon diodes with a forward voltage drop of 0.7 V are used in the given clipping circuit.

The diodes are arranged such that D₁ is connected to a –1 V source and D₂ is connected to a +2 V source, with output voltage V_o taken from the junction between the resistor and the two diodes.

We need to find the range of input voltage V_i for which V_o = V_i, i.e., when both diodes are in OFF condition and do not affect the output.

Analysis:

Condition for D₁ (left diode) to turn ON:

D₁ conducts when anode-to-cathode voltage ≥ 0.7 V.

Anode of D₁ is at V_i, cathode is at –1 V.

So, \(V_i - (-1) \ge -0.7 \Rightarrow V_i \ge -0.7~\text{V}\)

To keep D₁ OFF: \(V_i < -0.3~\text{V}\)

Condition for D₂ (right diode) to turn ON:

D₂ conducts when cathode-to-anode voltage ≥ 0.7 V.

Cathode of D₂ is at V_i, anode is at +2 V.

So, \(V_i - 0.7 \ge 2 \Rightarrow V_i \ge 2.3~\text{V}\)

To keep D₂ OFF: \(V_i < 1.3~\text{V}\)

Result:

For both diodes to remain OFF (and hence V_o = V_i), the valid range is: