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The difference between NPN and PNP transistors is the easiest thing in electronics to memorize and the easiest to get wrong in the wiring. The symbols look nearly identical, and the two parts are wired differently in ways that punish a moment of inattention — an NPN and PNP swapped in a circuit can either … Read more

Switch on a capacitor-charging supply and the first few milliseconds carry a surge that dwarfs the steady-state current: a rectifier fed into a discharged capacitor can briefly push ten times its rated average, and that first charge pulse is exactly what the surge rating on the diode datasheet is about. The IFSM number — forward … Read more

A rectifier datasheet is a dense page of numbers, and most engineers read it in the wrong order — jumping to the current rating and ignoring everything else until a failure forces a return visit. The numbers are easier to remember when you frame them as the datasheet’s answer to three questions: how much voltage … Read more

Relay circuits fail in the same surprising way over and over: the coil is fine, the switch is fine, everything reads correct on the bench — and the relay or the things around it keep dying. The usual culprit is the inductive kickback from the coil, and the usual fix is a flyback diode. But … Read more

Protection components are the least exciting parts of a board and the ones most often chosen by habit. A designer reaches for a TVS because the last board had one, or a Zener because a tutorial mentioned it, and both can be wrong on a 12 V rail — not because the parts are bad … Read more

The most confusing failures in a rectifier supply are the ones that look like a capacitor problem and turn out to be a bridge problem, or the reverse. A sagging DC output, a hot filter capacitor, a fuse that keeps blowing — each symptom can be produced by the bridge, the capacitor, or the two … Read more

The choice between a unidirectional and a bidirectional TVS is not a preference — it is decided by the protection zone the device guards. A TVS clamped line-to-ground on a rail that only ever swings positive can be unidirectional, with one junction and a single polarity to mount; a TVS guarding a differential line that … Read more

A MOSFET and a BJT can both switch the same load in many circuits, and choosing between them comes down to what the rest of the circuit asks. The BJT is a current-controlled valve: it turns on with base current, and its on-state drop stays relatively fixed. The MOSFET is a voltage-controlled gate: it turns … Read more

Welding and induction heating are the harshest IGBT duties outside the motor drive, because both throw high-current pulses at the device faster and harder than a steady load ever does. A welder draws a current spike at every arc strike; an induction heater switches at high frequency against an inductive coil. Both punish the IGBT … Read more

The four-diode bridge is the default rectifier topology for a reason, but it is not the only arrangement in the family. Center-tapped full-wave circuits, voltage-doubler stages, and common-cathode diode pairs all appear in real power supplies, and each one trades diodes, transformer windings, and stress in a different way. Understanding the family — what the … Read more

A bridge rectifier inside a power supply fails in one of a handful of ways, and the evidence is usually visible before a single meter lead touches the board. Burn patterns around the leads, a body split by thermal stress, a rail that sags after being fine, or smoke that only appears under load — … Read more