An unloaded zener regulator has a source voltage of 20 V, a series resistance of 330 W, and a zener voltage of 12 V, What is the Zener current? A. 28.4 mA B. 24.2 mA C. 34.4 mA D. 68.4 mA E. None of the above

The correct answer is: A. 28.4 mA

The zener current is the current that flows through the zener diode when it is in regulation. It is calculated by the following formula:

$I_Z = \frac{V_S – V_Z}{R_S}$

where:

• $I_Z$ is the zener current
• $V_S$ is the source voltage
• $V_Z$ is the zener voltage
• $R_S$ is the series resistance

In this case, we have:

• $V_S = 20\text{ V}$
• $V_Z = 12\text{ V}$
• $R_S = 330\Omega$

Therefore, the zener current is:

$I_Z = \frac{20\text{ V} – 12\text{ V}}{330\Omega} = 28.4\text{ mA}$

Option B is incorrect because it is the zener current when

the source voltage is 12 V. Option C is incorrect because it is the zener current when the series resistance is 12 V. Option D is incorrect because it is the zener current when the source voltage is 20 V and the series resistance is 12 V. Option E is incorrect because it is not a valid option.