ET 161 Linear Electronics

I. CATALOG DESCRIPTION:

ET161 Linear Electronics C 2, P 2, CR 3

The theory and applications of modern transistors are introduced; both the bipolar junction transistor and the field effect transistor are examined. Applications include usage in small and large signal class A amplifiers, as well as in class B power amplifiers. Voltage control FET applications are studied. Problem solving techniques involving digital computers are discussed.

Prerequisites: ET153 Introduction to Electronics, ET154 Computer Programming.
Corequisites: ET152 Circuits 2.

II. MATERIALS:

Text: Semiconductor Devices: Theory and Application, Fiore (pdf)
Lab Manual: Laboratory Manual for Semiconductor Devices, Fiore (pdf)

Tools: Scientific calculator, electronic hand tools and breadboard

 III. STUDENT LEARNING OUTCOMES:

The student will demonstrate familiarity with the operating principles and linear applications of bipolar and field effect transistors.

The student will demonstrate a working knowledge of the basic theory of device operation, how to properly bias devices, and have an understanding of common circuit applications including small and large signal audio amplifiers.

The student will use a mathematical and problem solving approach for design and analysis, based on fundamental DC and AC circuit principles and math concepts. This will include the use of computer simulations.

The student will demonstrate facility at constructing and trouble shooting transistor circuits in the laboratory with proper use of test equipment.

The student will demonstrate appropriate communication skills, particularly technical reports through the laboratory.

The student will demonstrate the ability to work as part of a technical team, particularly in the laboratory.

Course Assessment Standards

Syllabus

Background

Success in this course requires a good working knowledge of DC circuit principles, especially KVL and KCL. Thevenin and Superposition theorems are used quite a bit, although mesh and nodal analysis are generally not used. A basic working knowledge of diodes is assumed. AC analysis generally assumes "mid-band" frequencies, and thus phase is not usually considered (i.e., no complex impedances as found in ET152 Circuits 2). Math level is mostly algebra, although some equation proofs do require differential and/or integral calculus (not required for day-to-day calculations). For lab, you'll need the standard array of goodies as used in ET151 Circuits 1 and ET153 Intro to Electronics (breadboard, DMM, small handtools, hook-up leads, etc.) Unless otherwise specified, all lab exercises require a technical report due no later than one week after the exercise. Late penalty is one letter grade for the first half week, two letter grades for the second half week. Reports are not accepted beyond two weeks and receive a grade of 0. Remember, plagiarism is grounds for failure.

Free on-line resources covering a variety of electrical circuit topics and reference material may be found at: www.allaboutcircuits.com and www.talkingelectronics.com, in particular, check out this extensive free e-book that covers everything from basic semiconductor theory through diodes, transistors, amplifiers, modulation, power electronics and digital electronics, in nearly 800 pages. Also, here is an extensive on-line text from Analog Devices. See the home page for free circuit simulators.

The humorously inclined might enjoy Britney Spears' Guide to Semiconductor Physics

Week-by-week progress and assignments.
Please note that the text and laboratory manual are available as a single odt or pdf file at the bottom of this page.

1

We begin with an introduction to BJTs and the CE connection. This includes basic device parameters alpha and beta, and other data sheet items, simple DC BJT model, the need for biasing, simple biasing circuits (e.g., base bias) simple base biasing, DC load lines and saturation limits. We also look at LED driver circuits. Toward the end of the week we'll be looking at other forms of bias, including voltage divider bias and two-supply emitter bias.

  • Reading: By week's end, complete chapter 4.
  • Problems: Chapter 4: 1, 3, 5, 7, 9, 11, 13, 15, 19, 21.
  • Lab: As always, we start the semester with proper lab safety procedures. Our first experiment will be Base Bias. Items to note: Vbe should be fairly consistent at .7 volts, for all three transistors. Also, Ic >> Ib. Ic should vary among the three devices since it is highly unlikely that you'll pull out three with identical betas. Practical hint: although the main diagram shows two separate power supplies for Vcc and Vbb, only one supply is required since they use the same potential. Also, since several current and voltage measurements are needed for each iteration, it will be fastest if you dedicate two DMMs to current measurement (leaving them permanently wired), and a third to measure the various voltages. (Use one of the Fluke meters along with your own.)
2

We continue with bias variations, load lines, DC coupled circuits and PNPs. 

  • Reading: Compete through section 5.4 .
  • Problems: Chapter 5: 1, 3, 5, 7, 9, 21. Try the DC Bias Worksheet.
  • Lab: LED Driver Circuits. Items to note: Don't forget that the second circuit is in saturation, thus Vce is very small, perhaps .1 volts or so. Vce(sat) can be estimated from the saturation curves found on data sheets. We will look at how to do this in lab. Also, do not ignore VLED when computing Ic(sat). A reasonable value for the LEDs we use in lab is about 2.1 volts (don't use .7 volts- these are not silicon rectifying diodes!). Finally, note that circuit three, the non-saturating driver, can be unstable and might oscillate at high frequencies. This will throw off the readings on your DMM (it might, for example, indicate that Ve > Vb). Oscillation can be verified by using the 'scope. If your circuit oscillates, it can usually be cured by placing 1 uF caps from collector to ground. Make sure that you use good layout techniques.
3

We finish biasing. Once this is done, we'll have the first test.

  • Reading: Complete chapter 5.
  • Problems: Chapter 5: 19, 21, 23, 25, 30.
  • Lab: Voltage Divider Bias. Make sure that you measure beta for each transistor, either by using the curve tracer or by directly measuring base current (and then computing beta from Ic/Ib). For the lab write-up, compare the beta spreads versus the Ic spreads. Are the circuits stable in terms of Ic versus beta?
4

We tidy up biasing (going over the test) and introduce AC models and equivalent circuits. This is where the circuits start to get interesting. Biasing is sort of like learning how to make a car engine idle. Now it's time to start driving. We'll spend the next couple of months looking at small signal and large signal (i.e., power) amplifier circuits.

  • Reading: Chapter 6. Chapter 7 through section 7.2.
  • Problems: Chapter 6: 1, 3, 5, 6, 9, 11, 13. 
  • Lab: Emitter Bias. This is a very popular topology when dual polarity power supplies are present. It has the capability of producing very high collector current stability.
5

Our initial concern involves finding voltage gain, input impedance, and output impedance for typical voltage divider and dual supply emitter bias circuits. From here we will also look at the effects of source impedance and loads, and perhaps examine a few other biasing types for comparison.

  • Reading: Sections 7.3 and 7.4.
  • Problems: Chapter 7: 1, 2, 3, 4, 5, 9, 11. Start the Small Signal Worksheet. When you're done, have a cookie.
  • Lab: Feedback Biasing. This lab looks at a few of the lesser known biasing schemes. In your report, rank the circuits of figures in terms of stability of Ic relative to Beta. To do this, make sure you measure the Beta of each device (either by measuring base current or by using the curve tracer). Your discussion should include a theoretical analysis of why the circuits are ranked the way they are.
6

We continue with small signal AC analysis, introducing multi-stage schemes and direct-coupled circuits. If time permits, we will introduce emitter followers and darlingtons (otherwise, it gets bounced to next week).

  • Reading: Finish chapter 7.
  • Problems: Chapter 7: 15, 19, 21, 24. Finish problem set hand-out. Try the Monsterrific Problem. If you get this perfect, have two cookies.
  • Lab: PNP Transistors. This exercise examines PNP transistors in both biasing and LED driver configurations. Paying attention to voltage polarities and current directions is key.
7

We finish small signal work and we introduce large signal amplifiers. Finally, we get to drive loudspeakers.

  • Reading: Start chapter 8.
  • Problems: Chapter 8: 1, 3, 5, 7, 9.
  • Lab: Common Emitter Amplifier. This lab examines both gain and impedance including the effects of load and source resistances on gain. Two different circuits are employed, including a variation on voltage divider bias that can reduce the effects of power supply noise.
8

We continue work on class A amplifiers including AC load lines, load power, device ratings, efficiency, etc. Once this is done we have our second test.

  • Reading: Complete sections 1 through 5 of chapter 8.
  • Problems: Chapter 8: 15,17,18, 20. Try the Class A Worksheet.
  • Lab: Swamped Common Emitter Amplifier. This lab examines the effect of emitter swamping on gain, distortion, and input impedance. First of all, since you will have measured both the base voltage and the generator voltage in circuits, you can calculate an experimental Zin (just use the voltage divider rule backwards, where one resistor -Rsource- is known, and the other -Zin- isn't). Since all circuits have identical DC bias equivalents, you can directly compare their Zin values. Second, it is possible to see directly the reduction in distortion that swamping causes by turning the signal generator up until the output of the amplifier starts to clip. Do this and note the shape of the wave right before clipping occurs. A distortion analyzer will quantify the results nicely.
9

We start class B amplifiers. We pay particular attention to its advantages and disadvantages relative to class A operation.

  • Reading: Sections 1 and 2 of chapter 9.
  • Problems: Chapter 9: 1, 3, 5, 7, 9.
  • Lab: Voltage Follower. The basic idea of any voltage follower is one of load matching. Although a follower doesn't have any voltage gain (ideally unity), it does have current gain, and thus, power gain. Therefore, a high impedance source can be connected to a low impedance load without undue loss.
10

Work on class B is wrapped up, including circuits utilizing direct coupled drivers and loads. 

  • Reading: Section 3 of chapter 9.
  • Problems: Chapter 9: 11, 13, 15, 17, 19. Try the Power amplifier problem hand-out.
  • Lab: Class A Power Analysis. This lab looks at basic class A amplifiers and includes an examination of load power, device power, supplied power, and efficiency. It is important to note how low the efficiency is (for this circuit, well below the 25% theoretical maximum). Also, note how difficult it is to get a precise reading on the compliance due to the increase in distortion. It can be very instructive to investigate the effects of emitter degeneration (i.e., swamping). Although swamping will cause the gain to drop considerably, the class A distortion will drop dramatically, allowing a much more accurate viewing of compliance and clipping.
11

We begin Field Effect transistors, first with how JFETs differ from BJTs, and then we launch into JFET biasing.

  • Reading: Chapter 10. 
  • Problems: Chapter 10: 1, 3, 5, 7, 11, 15.
  • Lab: Class B Power Analysis. This is the class B output section most commercial amplifiers are based on. Pay particular attention to the bias stability gained by using a diode type bias. Also, note that notch distortion effects (i.e., crossover distortion) get worse as the signal is reduced (the exact opposite of what is seen with class A non-linearities).
12

JFET biasing is completed and AC amplifiers are introduced.

  • Reading: Chapter 11.
  • Problems:  Chapter 11: 1, 3, 5, 7, 9, 11, 13, 15.
  • Lab: Power Amp with Driver. This is a very useful design, complete with a class A direct coupled driver. Among other items, we will be examining the audibility of distortion using loudspeakers.
13

We finish JFETs and start with MOSFET circuitry, paying attention to the differences between MOSFETs and JFETs.

  • Reading: Chapter 12.
  • Problems: Chapter 12: 1, 3, 5, 7, 9, 11, 13, 15, 19. Try the FET problem set handout
  • Lab: JFET Bias. Unlike BJTs, FET biasing can be rather "troublesome". The reason is because we don't have a nice fixed .7 volt drop to rely on in one of the loops. Instead, since FETs have a reverse biased gate-source, Vgs is rather flexible and can be anywhere from 0 down to Vgs(off) (perhaps as low as -8 volts in some popular devices). As it turns out, absolute stability of Id is not generally required. Unlike BJTs, the gain characteristic (i.e., gm) will not be perfectly stable if the current is stable. For highest gain stability, some fluctuation of Id is in fact desired.

14

We wrap up with MOSFETs and look at a few interesting FET applications. Time permitting, we have our last in-class test.

  • Reading: Chapter 13.
  • Problems: Chapter 13: .1, 3, 5, 7, 9, 11, 13. When you're done, play some music and "dance with depraved abandon". Also, cookies might be in order.
  • Lab: JFET Amplifiers. Here we look at basic voltage amplifiers (common source topology) and source followers (common drain topology). Note how low the gains are when compared to their BJT counterparts. Of course, the FETs counter this by have much larger input impedance values. Zin can be found loosely through the voltage divider effect by placing a "sense" resistor in line with the gate terminal.

Resources

DC Bias Worksheet

Small Signal Worksheet

Monsterrific Problem

Class A Worksheet

Power Amplifier Problem

FET Problem Set


Text & Labs

Semiconductor Devices: Theory and Application (pdf)

Semiconductor Devices: Theory and Application (odt) 

Laboratory Manual for Semiconductor Devices (pdf)

Laboratory Manual for Semiconductor Devices (odt)

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2017 Jim Fiore