|
|
 |
How to Model a Zener Diode
Modeling zener diodes is not much more complicated than modeling LEDs. As with
LEDs, modeling is done using the diode primitive and the primary objective is to match
the reverse characteristic. To model a zener diode, set the diode model parameters to
the indicated data sheet values.
To model a zener diode, set the diode model parameters to the indicated data sheet
values.
|
| Model Parameters | Data Sheet Values |
| BV | VZ |
| IBV | IZT |
| RS | ZZT |
| RL | VR/IR |
| TBV1 | (TC in mV/C)/(BV*1000) |
| |
|
|
To simplify the process, consider the following test circuit.
|
This circuit, when run in DC analysis with the analysis limits shown below, plots the diode's reverse current vs. the reverse voltage, stepping the value of temperature from 0 to 127 in steps of 50 degrees.
|
The figure below shows what the DC analysis looks like for the MMSZ5221BT1 zener.
|
Note that Micro-Cap 6 adjusts the saturation current parameter, IS, to match the BV, IBV point exactly by taking into account the RS value.
For example, the RS of 30 in this case produces an additional drop when the diode current is at the IBV value of 20ma of 600mv, which, without compensation, would push the BV at 20ma to 2.4 + 600mv = 3.0 volts.
You can also add the CJO parameter from the C vs. nominal zener voltage curves, if they are given in the data sheet. Use the 0 volt bias curves.
|
|
|
|
|
