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Electrical track
Analog electronics

Transistors and op-amps, for real

The diode curve, biasing a BJT, common-emitter gain, MOSFETs as switches and resistors, op-amp amplifiers, comparators with hysteresis and split supplies.

FreeIn your browser2 courses, 27 lessons, about 14 hours
Start freeThe diode curveSee the course
Overview

How you will learn it

Analog is where many people get stuck: a transistor stops being a switch and becomes an amplifier, and the numbers start to matter. A simulator with a curve tracer and a scope makes it concrete, because you can change one resistor and watch the gain move.

Transistors and op-amps for real picks up after Electronics basics and takes each part from its curve to a working circuit, ending with the split supplies most op-amp designs use.

Outcomes

What you will learn

  • Read a diode curve and bias a BJT at a working point.
  • Design a common-emitter amplifier for a gain you choose.
  • Use a MOSFET as a switch and as a voltage-controlled resistor.
  • Build inverting and non-inverting amplifiers and comparators with hysteresis.
Your route

The courses and lessons to take

Every lesson opens in the editor right away, signed in or not, and the simulator checks each step.

  1. Step 1 · 7 lessons · 4 h

    Transistors and op-amps for real

    The whole course.

    1. 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.
    2. 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.
    3. 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.
    4. 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.
    5. 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.
    Every lesson in the course
  2. Step 2 · 20 lessons · 10 h

    Electronics basics

    New to transistors? The two basics lessons first.

    1. The transistor as a switchA tiny current into the base switches a big current through the collector. Switch an LED with a transistor and measure how much smaller the control current is.
    2. The op-amp: a gain you can chooseTwo resistors set the gain of an inverting op-amp amplifier. Turn a tiny wave into a big one, then push the gain until the top and bottom get chopped flat.
    Every lesson in the course
Keep going

Guides and tools on the same subject

Track

Electrical track

Current and voltage you can see, then transistors, op-amps, filters, power and PCBs. Every circuit runs in a real circuit simulator in your browser.

See the whole track
Questions

Questions people ask

What do I need before analog electronics?

Ohm's law, dividers and RC timing. Electronics basics covers all of them.

BJT or MOSFET?

Both appear in the course. BJTs are easier to see as amplifiers; MOSFETs are what most power switching uses. The course compares them on the same circuit.

Does the simulator show real op-amp limits?

Yes. The lessons show an LM358 clipping at its top rail on one 5 V supply and a TL072 losing its swing without the negative rail, so a design that ignores the supply shows it.