Question

A designer requires a shunt regulator of approximately 20 V. Two kinds of Zener diodes are available: 6.8-V devices with rz of 10 Ω and 5.1-V devices with rz of 30 Ω. For the two major choices possible, find the load regulation. In this calculation neglect the effect of the regulator resistance R.

(a) -30mV/mA and 120mV/mA respectively

(b) 30mV/mA and 60mV/mA respectively

(c) -60mV/mA and +60mV/mA respectively

(d) -30mV/mA and -120mV/mA respectively

This question was posed to me in my homework.

Origin of the question is Zener Diode in portion Diodes of Electronic Devices & Circuits

Answer 1

The correct option is (d) -30mV/mA and -120mV/mA respectively

To elaborate: Three 6.8v zeners provide 3*6.8 = 20.4v with 3 * 10 =30Ω Resistance, neglecting R, we have

load Regulation = -30mV/mA.

For 5.1 Zeners we need 4 diodes to provide 20.4v with 4 * 30 =120Ω Resistance.

load Regulation = -120mV/mA .