Why do we need a resistor in a Zener diode circuit, like in the diagram below?
I understand it is to limit the current but how so, and why do we need it for a Zener diode?
Does selecting different values of resistors affect the circuit performance? So when we are selecting a Zener diode we look in the specifications at different reverse currents that can flow through them. But if those can be changed through resistors, can we select any Zener diaode at a voltage, without looking at the maximum current?
Answer
Rather than going to 'no resistor' consider what happens if we just use resistors of different (lower) values and look at the pattern. As we reduce the resistor value the current through the zener will rise. Even if the voltage source is not perfect the power dissipated by the zener will cause it to fail due to overheating.
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