The component pages introduced resistors, capacitors, inductors, diodes, tubes, transistors, op-amps, transformers, and relays one at a time. Now we will begin combining a few of them into circuits that actually do useful work.
Cookbook rule #1: keep each circuit small
Each page will focus on one useful building block. Larger equipment is usually easier to understand when it is recognized as a collection of familiar small circuits.
Cookbook rule #2: follow the signal or current
Rather than staring at the whole schematic at once, find the input, follow the path one component at a time, and ask what each part contributes.
Cookbook rule #3: values are examples, not commandments
The resistor or capacitor values shown on these pages are chosen to make the circuit easy to understand. Real designs may need different values because of supply voltage, load, frequency, device tolerances, temperature, or other specifications.
Safety: some circuits — especially vacuum-tube circuits and power supplies — can involve dangerous voltages. The tube examples are for understanding circuit operation, not instructions for working on energized high-voltage equipment.
Look for familiar blocks inside unfamiliar equipment
A radio, amplifier, control board, or instrument may contain hundreds of parts, but many of those parts are arranged into recognizable sections: a voltage divider here, an RC filter there, a transistor switch, a buffer, an amplifier stage, a rectifier, or a relay driver.