Lab 3 - 2B 2010

Lab 3 - 2B 2010 - ECE 2B Lab #3 Lab 3 Transistors at DC...

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1 © Bob York ECE 2B Lab #3 Lab 3 Transistors at DC Overview In this lab you will experiment with the three types of transistors: JFETs, BJTs, and MOSFETs. Later coursework (ECE132) will teach you about the physics of how these devices work. Our goal in ECE2 is more practical and focused on using the devices: understanding their current-voltage characteristics, and learning how to configure the circuit environment for the transistor to set the appropriate biasing conditions. In this lab we will not build any clever functional circuits; the goal is simply to learn how to bias transistors correctly. This is always the first step in transistor circuit design, and is crucial to determining the success or failure of the circuit. In fact, most of the mistakes made by beginning students with transistor circuits can usually be traced to incorrect DC biasing. Table of Contents Pre-lab Preparation 2 Before Coming to the Lab 2 Parts List 2 Background information 3 Transistor Basics 3 Junction Field-Effect Transistors 3 Metal-Oxide-Semiconductor (MOS) Devices 5 Bipolar Junction Transistors 7 In-Lab Procedure 9 3.1 Depletion-mode FETs (JFET) 9 Measuring I-V characteristics 9 JFET Biasing Circuit 10 3.2 Enhancement-mode MOSFETs 11 Gate-Drain I D -V gs Characteristics 11 Four-Resistor Bias Circuit 12 Simple LED Blinker 13 More on Switching 13 3.3 CMOS Circuits 14 3.4 Bipolar Junction Transistors (BJTs) 16
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2 Transistors at DC © Bob York 2 Pre-lab Preparation Before Coming to the Lab Read through the lab experiment to familiarize yourself with the components and assembly sequence. Calculate the bias resistor values that are required in each of the steps. This will save you time during the lab experiment Each group should obtain a parts kit from the ECE Shop. Parts List Use stocked cabinet in lab and the bench decade box for any required resistors Laboratory #3 Intro to Transistors Qty Description 2 2N5485 n-ch JFET 2 2N7000 NMOS 2 2N3904 NPN BJT 2 2N3906 PNP BJT 1 CD4007 CMOS pair/inverter 1 1uF capacitor (electrolytic, 25V, radial) 2 Red LED (20mA)
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Background information 3 © Bob York 3 Background information Most of the popular Microelectronics texts will include essential FET and BJT concepts used in this lab (e.g. Neamen 3.1-3.2, 5.1-5.2, or Sedra & Smith 4.2-4.5, 5.2-5.5), although these are often somewhat more rigorous in detail than we need for our experiments. In what follows we summarize the basics needed in this lab. Transistor Basics Familiar two-terminal components such as resistors, capacitors, and diodes, are defined electrically by the current-voltage characteristic, () IV , as in Figure 3-1a. Transistors differ in that they include a third terminal, shown conceptually in Figure 3-1b, which serves as a control point to manipulate the current flow through the device. The ability to control the current flow through one part of the device using a separate electrical signal is what makes transistors useful.
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Lab 3 - 2B 2010 - ECE 2B Lab #3 Lab 3 Transistors at DC...

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