EE 321 Lab
Prelab for Lab 6: DIODES AND ZENER DIODES CIRCUITS

1) Consider the zener regulator shown in Figure 3.34 in Sedra and Smith.

• Find R so that the zener current will be equal to 20 mA with no load (use the conditions of part 1 of the lab).
• Add a 1 k load to the circuit. Calculate the current in the load and the zener. If the zener resistance rz = 10 ohms, how much will Vo change.
• Find the spec for rz.
• What is the load regulation with rz from the spec sheet.
• What is the largest load current this regulator can deliver and still have at least 1 mA in the zener? What load resistance does this imply?
• What is the line regulation with rz from the spec sheet.

2) Consider the precision voltage source in Figure 1.

• Find R to give the proper gain (4.2 v in and 10.0 V out) with the pot set a its mid point.
• The circuit appears to have positive feedback. Why doesn't it? Hint - if the output changes will the voltage at pin 3 change?

3) In the spec sheet find the voltage of a 4.3 V zener with only 0.1 mA (look at fig 11, the 4.3 V zener has 4.3 V at 20 mA).