December 2019 StudentZone Quiz Solution

Question 1:

Using the circuit in Figure 1. compute the resistance R_L for which V_L value is at 20% of the Zener voltage V_Z.

Answer 1:

First, we obtain the necessary values from 1N4735 datasheet:

• Zener Nominal Voltage: 6.2V

We can compute now the desired value for V_L:

At 1.24V voltage drop, the Zener diode is off (high impedance state, no current flowing though it), therefore the circuit becomes a simple resistive divider.

Knowing the differential input voltage V_IN=10V, R_s=1KΩ we can compute R_L as follows:

Corrected formula
[edited by: bsiegel at 12:41 PM (GMT 0) on 13 Jan 2020]