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3.3V Zener Diode 1N4728A

Zener Diode Pin Configuration

Pin No.

Pin Name




Current always Enters through Anode



Current always Exits through Cathode



  • Nominal Zener Voltage (VZ): 3.3V
  • Power dissipation (PZ): 500mW
  • Zener current (IZT): 76mA
  • Package: DO-35

Note: Complete technical details can be found in the 1N4728A Zener Diode datasheet given at the end of this page.


1N4728A Equivalent Zener Diodes:

4.7V Zener, 5.1V Zener, 6.8V Zener, 7.5V Zener, 15V Zener


How to select a Zener Diode:

A Zener diode is another form of diode, but is used for entirely different purpose. They are mainly used in protection circuits or as crude voltage regulators. Let us see how we can select one for your application.

There are two main parameters that are to be checked while selecting a Zener diode. One is the Zener Voltage and the other is Power dissipation. The Zener voltage is the voltage which appears across the Zener diode when a higher reverse potential voltage is applied to it. In regulator circuits it is this voltage (Zener voltage) which will be regulated and in protection circuit it is this voltage (Zener voltage) more than which the circuit is protected. The power dissipation decides the amount of current that can flow through the diode. Higher the power dissipation higher the current can flow.


How to use a Zener Diode:

As said a Zener diode will mostly be used in a protection circuit or in a crude voltage regulator circuit. Either way, it very important to remember that a Zener diode should always be used along with a Zener resistor.

A Zener resistor is nothing but an ordinary resistor which is used for current limiting purpose. This resistor decides (limits) the amount of current that can flow through the Zener diode or through the load connected to Zener diode; this was the Zener diode is protected from high current. If this resistor is not used the diode will be damaged due to high current.


In the above circuit the formulae to calculate the Zener series resistor Rs is shown below-

Rs = (Vs – Vz) / Iz

For a 1N4728A Zener diode the value of Vz is 3.3V and Pz is 500mW as mentioned in specifications above, now with supply voltage (Vs) of 12V the value of Rs will be:

Rs = (12-3.3)/Iz
Iz = Pz/Vz = 500mW / 3.3V = ~151mA
Therefore, Rs = (12-3.3)/151 = 0.0576 = 57 ohms
Rs = 60ohms (approx)


Applications of Zener Diode

  • Used in Voltage protection circuits
  • Can be used as low current voltage regulator
  • Input voltage protection for Microcontrollers or other ICs
  • Voltage stabilizing circuits


2D Representation (DO-41):

3.3V Zener Diode 1N47 Dimensions

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