A Zener diode is used as a 4 V voltage regulator in the circuit shown. Given that the diode requires a minimum current of 4 mA for voltage regulation, the maximum current (in milliamperes) permitted to flow through the load \( R_L \) is _________ (round off to one decimal place)
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In Zener diode voltage regulation circuits, the maximum current through the load is determined by the voltage difference across the resistor and the total current allowed by the Zener diode.
We are given:
- Voltage across the Zener diode \( V_Z = 4 \, \text{V} \),
- Supply voltage \( V_s = 16 \, \text{V} \),
- Resistor \( R = 1200 \, \Omega \),
- Minimum current for voltage regulation \( I_{\text{min}} = 4 \, \text{mA} \).
First, calculate the current through the resistor \( R \) when the load is at the minimum voltage regulation current:
\[
I_R = \frac{V_s - V_Z}{R} = \frac{16 - 4}{1200} = \frac{12}{1200} = 0.01 \, \text{A} = 10 \, \text{mA}.
\]
Now, to calculate the maximum current, we consider that the total current through the load \( R_L \) can be the current through the resistor plus the current that can flow through the Zener diode:
- At maximum current, the diode would supply its maximum current (since it is maintaining the 4 V voltage), so the maximum current is:
\[
I_{\text{max}} = 10 \, \text{mA} + 4 \, \text{mA} = 14 \, \text{mA}.
\]
Thus, the maximum current permitted to flow through the load is \( 6.0 \, \text{mA} \).
