Govt. Exams
Entrance Exams
From Acl = A/(1 + Aβ), we get 10 = A/(1 + A×0.1). Solving: 10(1 + 0.1A) = A → 10 = 0.9A → A ≈ 1000 (for high gain).
CMRR (dB) = 20 log₁₀(Ad/Ac); 80 = 20 log₁₀(ratio), therefore ratio = 10^(80/20) = 10^4 = 10000.
Voltage gain = gm × Rc (where Rc ≈ output impedance) = 0.04 × 50k = 2000 for a CE amplifier configuration.
Thermal stability improved by: (1) RE without bypass for DC stabilization, (2) lower supply voltage, (3) smaller β transistor, (4) heat sinking. VBE decreases with temperature (negative TC), increasing base current and ICO, causing thermal runaway.
Barkhausen criterion: For sustained oscillations, |Aβ| = 1 (unity gain) AND total phase shift = 0° (or 360°). Both conditions must be satisfied simultaneously.
Negative feedback reduces gain by factor (1+Aβ) but provides benefits: improved linearity, reduced distortion, increased input impedance (series feedback), decreased output impedance (shunt feedback).
Miller effect refers to the multiplication of base-collector capacitance by (1+Av) at the input, increasing input capacitance, reducing input impedance, and decreasing bandwidth.
Using K-map for three variables: (A'BC) + (AB'C) + (ABC') = C(A'B + AB') + ABC' = C(A ⊕ B) + ABC'. This represents XOR operation with an additional term, which is the minimal form requiring fewer gates than other options.
Ideal speedup in pipelining equals the number of pipeline stages. With 5 stages and optimal conditions, speedup is approximately 5x.
Maximum frequency = 1 / (propagation delay) = 1 / 50 ns = 1 / (50 × 10^-9 s) = 20 MHz.
