Electronic Fundamentals
Core concepts
This domain covers semiconductor devices and their aircraft applications. Know diodes (forward and reverse bias, rectification, zener regulation), bipolar transistors as switches and amplifiers (base, collector, emitter; NPN and PNP), field-effect transistors, thyristors, and integrated circuits. Understand operational amplifiers in basic configurations (inverting, non-inverting, comparator), oscillators, filters, and printed circuit board practices including ESD protection and soldering.
Traps to watch
- Diode drop: a silicon diode conducts at about 0.6–0.7 V forward; it is not a perfect switch.
- Transistor regions: cutoff (off), saturation (fully on switch), active (amplifier). Confusing saturation with active is a common distractor.
- NPN vs PNP: NPN turns on with base positive relative to emitter; PNP is the reverse.
- Zener orientation: operated in reverse breakdown to regulate voltage.
- ESD: static damage may be latent; always use wrist straps and grounded mats when handling CMOS.
- Op-amp ideal assumptions: infinite input impedance, zero output impedance, very high open-loop gain.
Worked example
A transistor with V_BE = 0.7 V is driven from a 5 V source through a 4.3 kΩ base resistor. Base current I_B = (5 − 0.7) ÷ 4300 ≈ 1 mA. If h_FE = 100, the maximum collector current in the active region is about 100 mA; if the collector load would demand more, the device saturates.
Rule of thumb
Ask "is it being used as a switch or an amplifier?" first. That single question resolves most transistor and op-amp questions.