# In a Zener regulated power supply a Zener diode with Vz = 6.0 V is used for regulation. The load current is to be 4.0 mA and the unregulated input is 10.0 V. What should be the value of series resistor Rs?

Grade:12

## 1 Answers

Mallikarjun Maram
50 Points
9 years ago
This problem is an example problem in NCERT class XII text book.  I have copy pasted the solution below:

The value of RS  should be such that the current through the Zener diode is much larger than the load current. This is to have good load regulation. Choose Zener current as five times the load current, i.e.,IZ = 20 mA. The total current through RS is, therefore, 24 mA. The voltage drop across RS  is 10.0 – 6.0 = 4.0 V.  This gives RS  = 4.0V/(24 × 10–3) A = 167 Ω. The nearest value of carbon resistor is 150 Ω. So, a series resistor of 150 Ω is appropriate.
Note that slight variation in the value of the resistor does not matter, what is important
is that the current IZ should be sufficiently larger than IL.

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