Zener diode "biasing current"

[eem2am]

bzx284 izmin

hello

for BZX284 C33 = 33V Zener diode..........

**broken link removed**

what "biasing current" has to flow through it to to allow it to give its Zener voltage between its anode and cathode?

for example, would say 1mA flowing through it allow it to have 33V across it.?

 

[hemant03]

zener diode biasing

That's not how the zener will work.
All you need to do to trigger is to ensure voltage across zener exceeds 33V.
It is generally used to protect the circuitry against voltage surges.

Thanks,
- Hemant

 

[FvM]

That's not how the zener will work.

I can work exactly like that, if it's used as a voltage reference.
As the datasheet shows, nominal zener voltage is specified for a 2 mA bias current Iz. The dynamic resistance specification also gives an estimation of the Vz/Iz dependancy. A zener diode can be operated also at considerably lower and fairly higher currents, the characteristic is generally following an exponential function.

 

[barry]

It is NOT 'generally used to protect the circuit". When used as a reference you should generally use the suggested (2ma) current. If the current gets too low, the device will be operating on the steep part of its V-I curve (small change in current causes a big change in voltage). If the current is too high, you're just wasting power. Rule of thumb for zeners in general (if no 'optimum' bias current is specified) is to bias the device so it is dissipating about 10% of its rated power.

 

[BABESH]

You need to supply Izmin to enable zener to maintain its stated zener voltage.

So connect a resistor Rs in series to Zener Cathode and Vin,
Rs=(Vin-Vz)/(Izmin+IL);
IL is the current drawn from the zener 33V reference.