Why does my circuit work on a breadboard but not on a PCB?

Short Answer: Breadboard capacitance and inductance accidentally filter noise that your PCB doesn't — or vice versa.

Detailed: Breadboards have:

• 5–15 pF capacitance between adjacent rows

• Parasitic inductance from long jumper wires

• Higher contact resistance (0.1–1 Ω per connection)

These "hidden components" can accidentally fix problems — or hide them.

Problem hidden on breadboard	Revealed on PCB
Missing decoupling capacitors	Breadboard capacitance acts as bypass cap
High-frequency oscillation	Breadboard inductance slows edges
Ground loops	Breadboard has one common bus
Signal integrity issues	Short PCB traces have less capacitance

Common PCB failures after breadboard:

• Oscillation (add 0.1 µF caps near every IC)

• Cross-talk between adjacent traces (separate analog/digital)

• Voltage drop on thin traces (use wider power traces or pours)

• Ground bounce (use ground plane, star ground)

The rule: After breadboard, add extra decoupling capacitors (0.1 µF per IC) and use a ground plane on PCB. What worked on a breadboard often needs more help on PCB.