PCB Schematic Symbols: The Complete Visual Reference (100+ Symbols)

How many different symbols can appear in a single schematic? On a complex PCB design, the answer can easily exceed two hundred. Miss one unfamiliar symbol and your entire build can go wrong — a reversed diode, a misread ground type, a logic gate wired backwards.

This guide covers 100+ PCB schematic symbols, organized into 9 categories, with side-by-side IEC 60617 and ANSI/IEEE 315 diagrams for every component that differs between the two standards. Whether you're a student reading your first schematic or an engineer cross-checking an unfamiliar notation, bookmark this page as your go-to visual reference.

1. Table of Contents
2. Passive Component Symbols
3. Semiconductor Symbols
4. Power and Ground Symbols
5. Logic Gate and Digital Circuit Symbols
6. Connector and Mechanical Symbols
7. Voltage and Current Source Symbols
8. Reading PCB Symbols in EDA Software
9. The 5 Most Commonly Confused Symbol Pairs
10. Free Downloadable Symbol Reference

Why PCB Symbols Matter — and How They Differ From Footprints

Before diving into the symbols themselves, one distinction trips up nearly every beginner: a schematic symbol is not the same as a PCB footprint.

IEC 60617 vs. ANSI/IEEE 315

• IEC 60617 — dominant in Europe, Asia, and most modern EDA libraries. Prefers rectangular boxes for complex parts.
• ANSI/IEEE 315 — common in North America and older documentation. Uses distinctive shapes (zigzag for resistors, curved arcs for inductors).

Throughout this article, every symbol that differs between the two standards is shown as an IEC | ANSI pair. Where both agree, one image is shown.

Section 1: Passive Component Symbols

1.1 Resistors

1.2 Capacitors

Internal link → Capacitor Symbol Guide

1.3 Inductors and Transformers

1.4 Crystal Oscillators and Resonators

Section 2: Semiconductor Symbols

2.1 Diodes

2.2 Bipolar Junction Transistors (BJT)

2.3 MOSFETs

2.4 Other Semiconductors

Section 3: Power and Ground Symbols

3.1 Power Supply Rail Symbols

3.2 Ground Symbols — Do Not Mix These Up

This is the single most common schematic error. Four ground symbols exist for a reason — they represent electrically isolated return paths.

Section 4: Logic Gate and Digital Circuit Symbols

4.1 Basic Gates

4.2 Flip-Flops and Latches

4.3 Multiplexers, Decoders, and Bus Symbols

Section 5: Connector and Mechanical Symbols

5.1 Connector Symbols

5.2 Switches

5.3 Test Points, Fuses, and Other Mechanical Elements

Internal link → What Do Multimeter Symbols Mean?

Section 6: Voltage and Current Source Symbols

Section 7: Reading PCB Symbols in EDA Software

7.1 Symbol Libraries by Software

Internal link → Top 10 Free PCB Design Software in 2026

7.2 Symbol Naming Conventions

Consistent naming prevents linking errors when assigning footprints. Best practices:

• Use the manufacturer part number as the base (e.g., STM32F103C8T6)
• Append the package in parentheses (e.g., LQFP-48)
• Prefix generic parts with their value: R_10k, C_100nF_X7R
• Keep pin numbers consistent with the datasheet, not with physical position on the symbol

Section 8: The 5 Most Commonly Confused Symbol Pairs

Even experienced engineers pause on these. Know them cold.

Section 9: Free Downloadable Symbol Reference

PCB Schematic Symbols Quick Reference Card (PDF)

Get a printable A4/Letter reference card covering all 100+ symbols in this guide, organized by category, with IEC and ANSI variants.

What's included in the PDF:

• Passive components — resistors, capacitors, inductors, crystals
• Semiconductors — diodes, BJTs, MOSFETs, thyristors
• Power and ground symbol types
• Logic gates — ANSI distinctive shapes and IEC rectangles
• Connector and switch symbols
• The 5 common confusion pairs with annotations

[Download Free PDF Reference Card →] (email opt-in or direct download)

Ready to Turn Your Schematic Into a Real PCB?

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• Instant online quote — upload your Gerber files and get pricing in seconds
• 24-hour prototype turnaround — for time-critical projects
• Full PCBA service — component sourcing and board assembly

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Frequently Asked Questions

What is the difference between a PCB symbol and a footprint?

A schematic symbol represents the electrical function of a component — what you place in a schematic diagram. A footprint represents the physical shape on the PCB — the pad pattern the component solders onto. In EDA tools like KiCad or Altium, each component links one symbol to one or more footprints, stored in separate libraries and edited with separate tools.

Which schematic symbol standard should I use: IEC or ANSI?

It depends on your region and industry. IEC 60617 is the international standard required by most European and Asian companies, and ISO-compliant documentation. ANSI/IEEE 315 is common in North American companies and older documentation. For personal and open-source projects, pick one and stay consistent. When submitting designs professionally, follow the company style guide or ask your client.

Where can I find free PCB schematic symbol libraries?

The best free sources are: (1) KiCad's official library on GitHub (10,000+ parts, actively maintained), (2) SnapEDA — free component search with symbols and footprints, (3) Ultra Librarian — free downloads for registered users, and (4) Component manufacturer websites — many publish KiCad or Altium library files directly on their product pages.

How do I read a PCB schematic if I'm a beginner?

Start by identifying the power rails (VCC, GND) to understand voltage domains. Then trace the signal path: follow wires from inputs (connectors, sensors) through active components (ICs, transistors) to outputs (displays, actuators). Reference designators (R1, C3, U4) correspond to the Bill of Materials. Net labels show that two non-adjacent wire segments are the same electrical node even when not visually connected.

What does a filled circle mean on a schematic?

A filled (solid) circle at a wire junction means the two wires are electrically connected — called a “junction dot.” Wires that cross without a dot are not connected. Some older schematics use a small bridge arc to indicate non-connection at a crossing. Always check which convention the schematic uses.

What does a bubble on a logic gate terminal mean?

A small circle (bubble) on a logic gate input or output indicates inversion. An output bubble means the signal is the logical complement of the gate's expression — that's how NAND is drawn as AND + output bubble, and NOR as OR + output bubble. An input bubble means the gate activates on a LOW signal at that pin (active-low enable).

Can I use the same ground symbol for analog and digital circuits?

No. AGND and DGND may connect at a single star point near the power supply, but they must be drawn and routed separately. Using one shared symbol signals to the PCB designer that the grounds are common everywhere, which causes shared return currents, noise coupling on ADC inputs, and EMC failures.

Summary

You've now seen all 9 categories of PCB schematic symbols:

1. Passive components — resistors, capacitors, inductors, crystals
2. Semiconductors — the diode family, BJTs, MOSFETs, thyristors
3. Power and ground — rail symbols, five types of GND
4. Logic gates and digital circuits — 8 gates, flip-flops, bus notation
5. Connectors and switches — headers, push-buttons, DIP switches
6. Voltage and current sources — DC, AC, controlled sources
7. EDA software libraries — where to find and create symbols
8. The 5 confusion pairs — the mistakes engineers make most
9. Free downloadable reference — printable PDF card

Download the quick-reference card to keep all 100+ symbols at your fingertips, and when you're ready to fabricate, get an instant PCB quote from NextPCB →

Related articles:
→ Capacitor Symbol: Every Type Explained with Diagrams
→ Complete Guide to Electrical and Electronic Symbols
→ Multimeter Symbols Explained
→ Top 10 Free PCB Design Software in 2026