**Today’s session addresses some of the problems encountered practically testing the forward and reverse bias characteristics of a zener diode. You will recall that there were essentially 2 major issues:**

- Non or partial functionality of decade resistance boxes
- Blown fuses in ammeters used to measure the zener current

The aim of this session is to design an alternative test circuit which provides valid and consistent results reliably.

**By the end of this session the learner should be able to:**

- Name the key components of the test circuit and explain their function
- Design a test circuit to measure the reverse bias characteristic of a given 5V1 Zener diode
- Build and test the circuit on breadboard, gather the results and plot a graph showing the conduction characteristic
- Compare the test specification of the alternative circuit with the original test specification
- Prepare a report which specifically compares both test specifications in terms of their ability to gather results which are valid, consistent, accurate and reliable
- Evaluate the session

The work carried out in this session will count towards the following outcomes:

*Unit 6 Pass 3 (This outcome will be complete by the end of the session)**Unit 53 Pass 4 Complete**Unit 35 Pass 2 Partially complete*

**Activity 1 (30 minutes)**

Each team to spend 15 minutes researching the following key areas. Then feedback to the group based on the results of their research (2 minutes each group):

- The history of TTL (Key figures, applications)
- The history of CMOS (Key figures, applications)
- The construction of a MOSFET
- The basic operation of an n channel MOSFET (enhancement mode)
- The basic theory of operation of a zener diode
- Operating point
- Voltage dividers

**Activity 2 (20 minutes)**

From the preceeding presentations, research and your own experience of conducting this type of test, write down everything you know about the following components and measurement equipment:

- 36NF06 N Channel MOSFET
- 220k Potentiometer
- 5V1 Zener Diode
- 2.2k Resistor
- Voltmeter
- Ammeter

Hint!! You will need to use online datasheets for some of the component connections.

Use the information and attempt to design a circuit that can measure the voltage across and current flowing through the 5V1 zener diode as it approaches and passes its reverse breakdown point.

**Activity 3 (1 hour)**

- Build the completed design on breadboard
- Conduct the test and gather the results (refer to previous test for given parameters)
- Simulate the test in Multisim
- Tabulate the results and plot a graph
- Compare the graph with the simulation and results on the datasheet

**Activity 4**

- Discuss your results as a team
- Draw up a test specification for the experiment you have just carried out
- Compile a report on the activities carried out. You should specifically compare the new test specification with last weeks in terms of validity, consistency, accuracay and reliability