Mnemonic 1: Dopants

"PeNTa for N-type, TRIo for P-type"

• PENTAvalent (5 electrons) → N-type (extra electrons = Negative carriers)
• TRIvalent (3 electrons) → P-type (holes = Positive carriers)

Examples: "Phosphorus, Arsenic, Sbismuth → PASses electrons → N-type" "Boron, Aluminum, Gallium → BAG holes → P-type"

Mnemonic 2: Special Diode Bias Conditions

"ZR – PR – LF – SN" (Zip-Rip – Lip-Flip – Sniff)

• Zener = Reverse (voltage regulator)
• Photodiode = Reverse (light detector)
• LED = Forward (light emitter)
• Solar cell = No bias (generates its own EMF)

Visual: "Z and P hide in the Rear (reverse bias); LED steps Forward; Solar flies Naturally"

Mnemonic 3: Band Gaps

"Si One-One, Ge Zero-Six-Seven, Diamond Five-Four"

• Si = 1.1 eV (one-one)
• Ge = 0.67 eV (zero-six-seven)
• Diamond = 5.4 eV (five-four)
• Barrier: Si = 0.7 V (Si SEVEN-tenth), Ge = 0.3 V (Ge THREE-tenth)

Mnemonic 4: Universal Gates

"NAND and NOR — Neither Nor: BOTH Universal" Both NAND and NOR are universal. The mnemonic plays on "Neither...Nor" — you can't say "neither NAND nor NOR is universal" because BOTH are!

Mnemonic 5: NOR Truth Table

"NOR is NObody Registers (output 1) unless No One speaks (all inputs 0)" NOR output = 1 ONLY when ALL inputs = 0. One active input (1) → output goes 0.

Mnemonic 6: De Morgan's Theorems

"Break the bar, change the sign"

• $\overline{A+B}$ → break the long bar → $\overline{A} \cdot \overline{B}$ (+ becomes ·)
• $\overline{A \cdot B}$ → break the long bar → $\overline{A} + \overline{B}$ (· becomes +) Breaking the bar always flips AND↔OR.