Problem Solving

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

Problem Solving Session PP

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





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