Question

A 10V zener diode along with a series resistance is connected across a 40V supply. Calculate the minimum value of the resistance required, if the maximum zener current is 50 mA.

Answer 1

From the figure we find that

V_i = 40V, I₁ = 50 mA

∴ Maximum current

I = I₁ + I₂ = 5mA + 0

= 50 mA = 50 x 10^-3 A

Since maximum current flows through zener diode, hence

I₂ = 0

Voltage drop across zener, V₀ = 10 V

Since I is maximum, hence maximum value of R is given by

R = \(\frac{V_i - V_0}{I} = \frac{40 - 10 }{50 \times 10^{-3}} \) = 60Ω