I've been learning about using zener diodes to generate a reference voltage for a small comparator circuit, the intention is to detect when a motorcycle battery is charging (i.e more than 13v), and use that to activate an Arduino circuit with a relatively high draw of 2A)
I've been fortunate enough to be given an example I can work from here on SX. However, something occured to me whilst learning about Zener diodes.
Once they are electrically closed, the input voltage has to be removed, before the open again. (speaking in terms of electrical continuity). To put that another way, once more than 12v (for a 12v 5A Zener) is seen, and the reverse bias breaks down, I (apparently) have to completely remove the input voltage in order to sever the connection.
Is that accurate, and is this expected, normal behaviour? I need to be able to power down my device when the voltage at the battery drops back down below 12v.
Best Answer
It occurs to me that you're thinking of a zener diode as a thyristor or a diac.
For example, the IV curve for a diac:
Once either threshold voltage is reached, the diac "turns on" and stays on until the current drops below the holding current value. Importantly, note that there are two values of current associated with any voltage between \$V_F\$ and \$V_{BO}\$ since the diac can be "on" or "off".
However, the IV curve for a zener (or avalanche) diode:
is qualitatively different. Note that, for the zener, for any voltage, there is only one value of current associated so the zener isn't a two-state device. Yes, it does have regions of operation (forward biased, reverse biased, and breakdown) but these simply refer to different regions of the IV curve.