Lesson plan

Transistors and op-amps for real lesson plan

Intermediate, after Electronics basics: the diode curve, biasing a BJT, common-emitter gain, the MOSFET as switch and resistor, op-amp gain both ways, comparators with hysteresis and split supplies.

3 chapters, 7 lessons, about 4 hours, no board. Every lesson runs in the browser, with nothing to install.

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The unit

Objectives and materials

By the end, students can

The diode curve, a BJT biased by hand, and the MOSFET both ways.
A transistor amplifier and an op-amp amplifier, each set by two resistors.
Clean decisions with hysteresis, and room on both sides of ground.

Materials for the whole unit

Capacitor
Full-size breadboard
Function generator
LED
LM358 dual op-amp
LM393 dual comparator
MOSFET
Multimeter x 3
Oscilloscope
Potentiometer
Resistor x 5
Slide switch
TL072 dual JFET op-amp
Transistor (NPN or PNP)

Every part is already on the simulator’s bench, so there is nothing to buy or hand out. The counts are the most any one lesson uses, if you build it on real breadboards too.

Chapter 1. About 1 h 40 min

Diodes and transistors

The diode curve, a BJT biased by hand, and the MOSFET both ways.

Lesson	Time	What students do
The diode curveA red LED on a bench supply with a 10 ohm sense resistor: almost no current below the knee, then a flood. Why a diode is not a fixed 2 V drop, and why every LED gets a resistor.	30 min	Run it and read the current Below the knee Past the knee Why every LED gets a resistor The diode that works backwards
Biasing a BJTA 2N2222 and an LED: hard on as a switch, then starved of base current until the collector current follows the base current a hundred and seventy times over. Picking a base resistor for the current you want.	35 min	A switch, driven hard Count the base current Starve the base It follows Bias it where you want it Why real circuits do not trust beta
MOSFET as a switch and as a resistorA 2N7000 with a knob on its gate: fully on with about 2 ohm left, fully off, and in between a resistor the gate voltage sets. Gate threshold, on resistance and why a MOSFET takes no gate current.	35 min	All the way on All the way off Find the threshold What is left when it is on A resistor you set with a voltage Logic level, and why a pin can drive it

Materials

Full-size breadboard
LED
MOSFET
Multimeter x 2
Potentiometer
Resistor x 2
Slide switch
Transistor (NPN or PNP)

Check for understanding

Each student finishes "MOSFET as a switch and as a resistor" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go.

Then ask each one to explain, in a sentence or two, the last thing it asked of them: "Logic level, and why a pin can drive it".

Chapter 2. About 1 h 5 min

Gain

A transistor amplifier and an op-amp amplifier, each set by two resistors.

Lesson	Time	What students do
Common-emitter gainA divider-biased 2N2222 amplifier on 9 V: read the operating point, measure a gain of about 4.5 with AC meters, halve it, clip it, and see what bad bias does.	35 min	Run it and read the bias Measure the gain Change the gain Push it too hard Bad bias What you can build with it
Inverting and non-inverting ampsAn LM358 amplifier on one 5 V supply, read with AC meters: a gain of 3.2 from two resistors, a gain of 2, a DC offset that pushes it into its top clip, and the inverting amplifier on paper.	30 min	Run it and read the input Non-inverting gain Set a gain of 2 The DC gets amplified too The inverting amplifier

Materials

Capacitor
Full-size breadboard
Function generator
LM358 dual op-amp
Multimeter x 3
Oscilloscope
Resistor x 4
Transistor (NPN or PNP)

Check for understanding

Each student finishes "Inverting and non-inverting amps" on their own, without opening the hints. The simulator checks 5 of its 5 steps as they go.

Then ask each one to explain, in a sentence or two, the last thing it asked of them: "The inverting amplifier".

Chapter 3. About 1 h 5 min

Real-world analog

Clean decisions with hysteresis, and room on both sides of ground.

Lesson	Time	What students do
Comparators and hysteresisAn LM393 comparing a knob with 2.5 V: an open-collector output, an LED that lights past the threshold, and one feedback resistor that gives it two thresholds so a noisy signal cannot make it chatter.	30 min	A one-bit decision An output that can only pull down Give it two thresholds And the way back down Make the gap bigger
Split suppliesA TL072 inverting amplifier on +12 V and -12 V: a gain of -4.7 on a signal centered on ground, a DC output below zero, what happens without the negative rail, more gain, and where it clips.	35 min	Run it Below ground Take the negative rail away More gain Find the ceiling What you have now

Materials

Full-size breadboard
Function generator
LED
LM393 dual comparator
Multimeter x 2
Oscilloscope
Potentiometer
Resistor x 5
TL072 dual JFET op-amp

Check for understanding

Each student finishes "Split supplies" on their own, without opening the hints. The simulator checks 6 of its 6 steps as they go.

Then ask each one to explain, in a sentence or two, the last thing it asked of them: "What you have now".

Your class

Teach this unit as a class

Start a class from this course and its 7 lessons are assigned in one go, in order. Students join with a six-character code or printed login cards, and each one’s work comes back to you.

The class tools are free for 30 days for one class of up to 20 students, with no card. The lessons themselves are free either way.

Start a class from this course See the demo class

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