Govt. Exams
Entrance Exams
For n select lines, 2^n inputs are possible. For 8 inputs: 2^n = 8, so n = 3. An 8:1 multiplexer needs 3 select lines (A, B, C).
Gray code (Reflected Binary Code) is designed such that successive values differ by only one bit. This is useful in error detection and mechanical encoders.
10110.101 = 1×16 + 0×8 + 1×4 + 1×2 + 0×1 + 1×0.5 + 0×0.25 + 1×0.125 = 16 + 4 + 2 + 0.5 + 0.125 = 22.625
AND gate can be implemented using two NAND gates. First NAND gate as AND, second NAND gate as NOT (both inputs same) to negate the output.
NAND gate output is 0 only when all inputs are 1. NAND is NOT of AND operation. For 2-input: output is 0 only when both inputs are 1.
XOR is a derived logic gate made from combination of basic gates (AND, OR, NOT). The three basic gates are AND, OR, and NOT.
Thermal voltage VT = kT/q, where k = 1.38×10⁻²³ J/K, T = 300K, q = 1.6×10⁻¹⁹ C. VT ≈ 26 mV at room temperature, a fundamental parameter in semiconductor device physics.
GaAs has electron mobility ~8500 cm²/Vs, significantly higher than Si (~1350 cm²/Vs), enabling higher frequency operation.
Pconduction = ID²·RDS(on) = (20)²×0.5 = 400×0.5 = 200 W
For p-channel: |VGS - VT| = |-8 - (-2)| = |-6| = 6 V overdrive, or algebraically VGS - VT = -8 - (-2) = -6 V
