Question

An ac voltage V_i = 12 sin(100 πt)V is applied between points A and B in a network of two ideal diodes and three resistors as shown in figure. During the positive half-cycle of the input voltage V_i supplied to the network.

1. Identify which of the two diodes will conduct and why?
2. Redraw an equivalent circuit diagram to show the flow of current.
3. Calculate the output voltage drops V₀ across the three resistors when the input voltage attains its peak value.

Answer 1

a. During positive half-cycle:

A is positive w.r.t. B.

Diode D₁ is reverse-biased.

Diode D₂ becomes forward-biased.

D₂ conducts because it is forward-biased.

b. 

c. Peak input voltage:

R_eq = `3/2` kΩ

I = `12/(3//2)`

= `(12 xx 2)/3`

= `24/3`

= 8 mA

R_(1Ω) = 1 × 4 mA

= 4 V

R_(2kΩ) = 2 kΩ × 4 mA

= 8 V

V_(3kΩ) = 4 mA × 3 kΩ

= 12 V