A 8 V Zener diode along with a series resistance R is connected across a 20 V supply (as shown in the figure). If the maximum Zener current is 25 mA, then the minimum value of R will be ____ Ω.
A 8 V Zener diode along with a series resistance R is connected across a 20 V supply (as shown in the figure). If the maximum Zener current is 25 mA, then the minimum value of R will be ____ Ω.
Correct Answer: 480
Approach Solution - 1
To find the minimum value of the series resistance R, we start by analyzing the circuit. The Zener diode maintains a constant voltage of 8 V across it when it is functioning in the breakdown region. Given the supply voltage is 20 V, the voltage across the series resistor R is:
VR = 20 V - 8 V = 12 V
The maximum Zener current, IZ, is 25 mA. Applying Ohm's law to the resistor:
IZ = VRR
Rearranging to find R:
R = VRIZ
Substituting the known values:
R = 12 \text{ V}{0.025 \text{ A}} = 480 \Omega
The minimum value of the series resistance R is confirmed to be 480 Ω, which fits within the expected range of 480 to 480 Ω.
Approach Solution -2
R will be minimum when RL is infinitely large, so
RZener=\(\frac{8}{25×10^{−3}}\)
RZener=320 Ω
So, \(\frac{R}{R_{Zener}}=\frac{12}{8}\)
R=\(\frac{12}{8}\)×320
R=480 Ω
So, the answer is 480 Ω.
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Electric Current
Defining Electric Current
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