Govt. Exams
Entrance Exams
Class AB uses a small quiescent current to bias transistors slightly into conduction, eliminating crossover distortion while maintaining better efficiency than Class A.
RC oscillators derive their frequency from RC time constants. The frequency f = 1/(2πRC) approximately, making RC the dominant parameter.
For inverting amplifier, Vo = -(Rf/Rin) × Vin = -(100k/10k) × 0.1 = -10 × 0.1 = -1 V.
Push-pull amplifiers use complementary transistors driven 180° out of phase to handle positive and negative half-cycles separately.
Class B achieves ~78.5% efficiency by conducting only 180° of the cycle compared to Class A's ~25% efficiency, though it introduces crossover distortion.
Colpitts oscillator uses capacitive voltage divider with two capacitors in series across an inductor for frequency-determining feedback.
For a non-inverting amplifier, Acl ≈ 1 + (Rf/Rin) = 1 + 10 = 11. The feedback dominates over the open-loop gain.
Maximum power transfer theorem states that maximum power is delivered when load impedance equals complex conjugate of source impedance, especially in AC circuits.
RC phase shift oscillator depends entirely on RC values which have poor tolerance and temperature coefficients, resulting in frequency drift.
Transimpedance gain = Vout/Iin = -Rf for inverting configuration. The feedback resistor directly sets the input-to-output conversion.
