# Sedra/Smith Ex. 3.17-18 Zener Diodes

#### Marit

Joined Sep 10, 2016
1
Hello!

I am trying to solve Ex. 3.17 and 3.18 in Sedra/Smith Microelectronic Circuits 7th edition.
In 3.17 I need help to find the maximum power of the zener diode. My teacher said to use P=V*I, but I can't figure out how. Maybe I need to find the rz resistans?

In 3.18 I need to find an expression for the line and load regulation. I have no load in this circuit. The regulation is expressed by deltaV, but my source is just V = 15 V constant, so that's where my problem starts.

Thank you!

#### AlbertHall

Joined Jun 4, 2014
8,789
3.17 Note that the question says that the zener voltage is constant for currents greater than five times the knee current. For such currents, what is the value of Rz?
When the load current is 0mA what is the zener voltage and zener current?
When the load is 15mA what is the zener voltage and zener current?
You can get the power dissipation in the zener for both conditions using P=V*I, where V=zener voltage and I=zener current.

3.18 For line regulation, calculate the output voltage for a different supply voltage, say 16V
For load regulation, calculate the output voltage if there is a load drawing, say 10mA.