| # | Common Error | What Students Think | Correct Understanding | How to Avoid |
|---|---|---|---|---|
| 1 | n-type is negatively charged | Extra electrons → negative charge | n-type is NEUTRAL; dopant adds proton (nucleus) AND electron equally | Remember: "n-type" = majority carrier type, not net charge |
| 2 | p-type is positively charged | Holes = positive charge on material | p-type is NEUTRAL; trivalent dopant has one fewer proton, one fewer electron | Both n and p types are always electrically neutral |
| 3 | Mass action law only for intrinsic | n_e × n_h = n_ seems like intrinsic formula | Applies to ALL semiconductors: intrinsic, n-type, p-type | The law is universal for a given material at given temperature |
| 4 | Zener diode in forward bias for regulation | Diodes work in forward bias → Zener must too | Zener operates in REVERSE bias at breakdown voltage V_Z | "Zener = Reverse bias for regulation" — its unique feature |
| 5 | Photodiode in forward bias | Needs bias to detect light → forward bias | Photodiode MUST be in reverse bias for fast response and linear detection | Reverse bias increases depletion width → faster e-h pair separation |
| 6 | Full-wave rectifier: f_out = f_in | Only converting AC to DC, frequency same | Full-wave: f_out = 2f_in (both half-cycles rectified) | Half-wave = same f; Full-wave = double f |
| 7 | NAND only is universal (not NOR) | NAND is more common → must be the only universal | BOTH NAND and NOR are universal gates | "Neither is more universal — BOTH are" |
| 8 | NOR output: 1 when all inputs are 1 | Confused with OR (which is 1 when any input is 1) | NOR output is 1 ONLY when ALL inputs are 0 | NOR = NOT OR → opposite of OR |
| 9 | Conductivity of semiconductor falls with temperature | Like metals (resistance increases) | Semiconductor conductivity INCREASES with temperature (negative temp coeff) | Semiconductors ≠ metals: thermal energy excites more across gap |
| 10 | Silicon and Germanium have same band gap | Both are semiconductors → similar properties | Si: E_g = 1.1 eV; Ge: E_g = 0.67 eV; different knee voltages (0.7 V vs 0.3 V) | Memorize exact values: Si = 1.1 eV / 0.7 V; Ge = 0.67 eV / 0.3 V |
Part of PH-03 — Semiconductors & Electronic Devices
Common Errors & Error Analysis
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