Source: https://mokxi.com/teachers/plans/analog-amplifiers Updated: 2026-11-11 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. Start a class from this course 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 curve A 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 BJT A 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 resistor A 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 gain A 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 amps An 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 hysteresis An 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 supplies A 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 More units ## Other lesson plans Electronics basics 20 lessons, about 10 h. Embedded on the Arduino Uno 16 lessons, about 12 h. Embedded on the ESP32-C3 13 lessons, about 11 h. Embedded on the Raspberry Pi Pico 7 lessons, about 6 h. Build your own fight stick 5 lessons, about 4 h. Embedded on the STM32F411 6 lessons, about 6 h. C++ on a board 13 lessons, about 10 h. Digital logic and memory 4 lessons, about 4 h. Interactive devices on the Uno 9 lessons, about 8 h. From gates to a computer 23 lessons, about 16 h. Build a claw machine 8 lessons, about 6 h. Every unit All the courses as ready-made units, on the teachers page.