Electronics Lab - Transistor Biasing

Electronics I and Lab

Transistor Biasing

Introduction:

Week 5 lab is based on the fundamentals of a transistor biasing and the analysis of the circuit.

The goal of Transistor Biasing is to establish a known Q-point in order for the transistor to work efficiently and produce an undistorted output signal. In bipolar transistor circuits, the Q-point is represented by ( VCE, IC ) for the NPN transistors or ( VEC, IC ) for PNP transistors.

Please review the following videos before getting started with this lab:

1. Watch the video: “Video 3: Fundamentals of breadboard”
2. Watch the video: “Video 4: Basic electrical components”
3. Watch the video: “Video 5: Simple resistive circuit with NI myDAQ”

Materials and Equipment:

Materials:

• Hardware Parts (In the Toolbox):
  • An NPN transistor: 2N3904
  • Four resistors: 1 kΩ, 470Ω, 3 kΩ and 6 kΩ
  • Jumper wires

Equipment:

• Hardware Equipment:
  • Breadboard
  • NI myDAQ Instrument device
  • Screw Driver
  • Screw Terminal connector
  • USB Cable
  • Multimeter with probes
  • Multimeter from NI ELVISmx Instrument Launcher

Procedure:

*** This lab has to be implemented only in hardware (using NI myDAQ) ***

1. Analyze the circuit in the Figure 1 below to calculate the following values: VBB, VE, IE, VC and VCE. Make sure to include 20% tolerance for each resistor in the calculations.
2. Construct the circuit shown in Figure 1 below on the breadboard using the transistor and two resistors (RCand RE).

Figure 1

1. Using the jumper wires, screw driver and screw terminal connector, connect the board to NI MyDAQ Instrument Device.
2. Use channel +15V pin out on the NI myDAQ Instrument Device to provide the supply voltage (VCC). Use channel AI0 to measure the required voltages: VBB, VE and VC and currents: IC and IE using the Multimeter.
3. Tabulate the data from step 1 and step 5.

 CalculatedMeasuredVBB  VE  VC  IE  IC  

1. Short the resistor R2 and calculate the values in steps 1.
2. Modify the circuit in Figure 1 to short the resistor R2 and measure the values in step 4.

 Measured values with R2 shortedVBB VE VC IE IC 

Review questions:

1. Compare a calculated and measured values in the table. Discuss whether the values are the same of different. If they are different, provide the reasoning. And how to reduce this difference between calculated and measured values.
2. What happens when R2 is shorted? Why does the measured values change?
3. If the NPN transistor is replaced with a PNP transistor, how does the change in the transistor effect the current and voltage in the circuit?

Deliverables:

1. Analysis of the circuit and calculations of voltages: VBB, VE and VC and currents: IC and IE.
2. Place your student ID card on the breadboard and take a picture of the circuit board and pin out on the NI myDAQ Instrument Device.
3. Take screenshots of the measurements obtained from function generator and Multimeter on the NI ELVISmx Instrument Launcher on your screen.

Lab Report:

• Use the Lab report template found in the “Tools and Template” link in the navigation center.
• Include all the deliverables.
• Include all the screenshots of the measurements from circuit design on the breadboard using NI myDAQ Instrument Device and measurements from MI ELVISmx Instrument Launcher.
• Save the document as Lab5YourGID.docx (ex: Lab5G00000000.docx) and submit in Blackboard.

Grading Rubrics

Grading CriteriaPointsAnalysis of the transistor circuit in Figure 1 using NPN transistor10Including 20% tolerances in the calculations10Construct the circuit in Figure 1 on the breadboard20Interfacing the breadboard with the NI myDAQ using appropriate pins10Measurement of the voltages: VBB, VE and VC and currents: IC and IE using the Multimeter probes10Analysis of the transistor circuit in Figure 1 with R2 shorted10Measurement of the voltages (with R2 shorted): VBB, VE and VC10Table and Review Questions10Report format (Proper use of template)10TOTAL100