# Wattage Rating for these Zeners

I have a circuit (Death of Zen audio amp) , which requires 2 12 volt zener diodes.
What is a safe wattage rating for them? Does this work?

$$\I_{z} = \frac{P_{z}} V_{z} \$$ where $$\I_{z}\$$ is zener current, $$\P_{z}\$$ is the power rating, and $$\V_{z}\$$ is the zener voltage. Small zeners are typically rated at 400mW and 1W. A 33V 400mW zener therefore has a maximum current of 12mA. Allowing for a resistor voltage drop of 5 to 7 volts means that the zener current will be 5 to 7 mA (1V across 1k gives 1mA). Since it is recommended that zeners be operated at between 5% and 80% of the maximum rated current, this fits very nicely into our requirements.