Question 1
A simple Zener diode shunt voltage regulator is to supply 12 V to a load which normally draws a load current which varies from 0 to 50 mA. The input voltage varies between 15 V and 18 V.
1.1 Calculate the maximum rated current value of a Zener device to be used.
1.2 Calculate the minimum power for the Zener that could be used safely.
1.3 If a 5 W rated Zener were to be used, calculate the range of possible RS. values and hence suggest a suitable standard E12 resistor value.
1.4 State four (4) conditions under which a Zener diode dissipates minimum power in a regulator circuit.
Question 2 (IEIIQ15)
A 2.5 W Zener diode is used in a simple Zener shunt voltage-regulator to supply 5.1 V to a load which normally draws a load current varying from 0 to 125 mA. The input voltage varies between 8 V and 9.5 V
2.1 Give two (2) reasons for the inclusion of the series resistor in the Zener-regulator circuit.
2.2 Calculate the range of series resistance that may safely be used in this circuit.
2.3 Select a single suitable standard E12 resistor value and give its colour code with 1 % tolerance.
