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December 2019 StudentZone Quiz Solution

Question 1:

Using the circuit in Figure 1. compute the resistance RL for which VL value is at 20% of the Zener voltage VZ.

Answer 1:

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

  • Zener Nominal Voltage: 6.2V

We can compute now the desired value for VL:

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 VIN=10V, Rs=1KΩ we can compute RL as follows:

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