Technical mental model

Diodes enforce directional current behavior, but real performance depends on forward drop, reverse stress limits, recovery behavior, and thermal loading.

Forward conduction is exponential at the device level, approximated as drop-plus-resistance in many practical designs.

Reverse blocking works until breakdown constraints are exceeded.

Diode family choice (Schottky, ultrafast, TVS) should match switching speed and protection goals.

Equations and constraints that drive decisions

Shockley diode equation (first-order model):

Where:

• $I_S$: saturation current
• $n$: ideality factor
• $V_T$: thermal voltage

Forward power dissipation estimate:

Implementation walkthrough

Implementation sequence:

1. Select reverse voltage and current ratings from worst-case transients, not nominal values.
2. Use flyback diode paths for inductive loads and validate clamp waveform.
3. Check thermal rise at sustained current.
4. For high-frequency switching, validate reverse-recovery impact on losses and EMI.

Validation and debugging checklist

• Polarity mistakes remain a frequent assembly/runtime issue.
• Under-rated reverse voltage can fail only during spikes, making bugs intermittent.
• Slow diodes in fast-switching paths increase heat and noise.
• Ignoring temperature dependence can invalidate margin assumptions.

Diode selection is robust when electrical stress, switching speed, and thermal behavior are all accounted for together.