Electronics Glossary

Electronics terms in plain language

Pull-up/down

Resistor to VCC/GND setting an input's idle logic level. Without it the input floats.

Debouncing

Filtering button contact bounce — in software (10–50 ms) or an RC network.

PWM

Variable duty pulses: average voltage = duty×Vcc. LED brightness, servos, motors.

ADC

Analog-to-digital converter: voltage → code. 10-bit = 1024 levels over the reference.

Voltage reference

Stable voltage for ADC/DAC. Internal often worse than external (TL431, REF50xx).

Decoupling

100 nF ceramic at every chip — local energy reservoir. Missing = glitchy MCUs.

ESR

Capacitor's equivalent series resistance. Aged electrolytes → high ESR → ripple, failures.

MOSFET

Voltage-controlled, not current. Load switch: logic-level gate for 3.3/5V drive.

Schottky diode

0.15–0.45V drop instead of 0.7V — less loss, faster. Reverse-polarity protection, OR-ing.

Zener diode

Reverse-biased holds a fixed voltage — crude regulator/input protection.

LDO vs DC-DC

LDO: simpler, cleaner, poor efficiency at high ΔU. DC-DC: 85–95% efficiency but noisy.

Open-drain

Output with no high side: pulls low or releases. Needs pull-up — I2C, buttons, level bridging.

I2C

Two wires (SDA+SCL), 7-bit addresses, pull-ups on both. Sensors, EEPROM, displays.

SPI

Four wires (MOSI/MISO/SCK/CS), faster than I2C, one CS per chip.

UART

Asynchronous serial TX/RX, baud must match. Console, GPS, GSM modems.

Differential pair

Signal over two antiphase wires — noise immunity: RS-485, CAN, USB, Ethernet.

Watchdog

Timer resetting a hung MCU — pet it in software or it resets.

Footprint

Pad pattern for a component on the board. Wrong footprint = part won't fit.