|Created||November 13, 2011|
|Last modified||May 17, 2012|
A Zener diode provides controlled reverse breakdown, and can act as a fixed voltage reference.
Zener diode D1 provides a fixed breakdown voltage of about 5.1 volts over a wide range of currents. R1 is necessary to prevent over-loading of voltage source V1.
Using a Zener diode like this isn't a particularly efficient way to generate a fixed voltage reference due to the high currents involved, but it's quite simple and reliable.
This circuit highlights several cool features of CircuitLab simulations that you can quickly try. Load this circuit with the "Open in editor" button above, and then click the "Simulate" tab to get started.
You can see the output voltage (near 5.1V) as well as the DC current running through the Zener diode -- those things can get quite hot!
Use the DC sweep to simulate how the output voltage will be affected if the input voltage changes. As you can see, the output remains quite close to 5.1V over many volts of input voltage.
You can plot the frequency response of this voltage reference, which might be useful if you have a noisy power supply (V1), and are curious to know how much of that noise makes it into the "regulated" voltage V(out). As you can see, with the current parameters, there's about -40dB gain between V(in) and V(out). This means that a ripple at the input will cause a ripple about 1/100th as big at the output -- not a bad start for power supply noise rejection.
how can current pass through the anode of zener? the direction is from cathode to anode
May 30, 2013
Try it! You will be impressed. A Zener in the reverse voltage mode will break down at the Vz value and start to conduct. Its current can vary but the voltage that is dropped across the zener will remain fairly constant at the Vz value. About 5% (not real good conpaired for todays advanced circuits) but as the auoher said, " this circuit works well and is very stable." That's how the zener works.
June 16, 2013
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