Govt. Exams
Entrance Exams
The voltage gain of a CS amplifier is Av = -gm × RD, where gm is transconductance and RD is the drain resistance. This is the fundamental relationship.
P = V²/R → V = √(P×R) = √(100×8) = √800 ≈ 28.3 V RMS.
Gain = Vout/Vin = 5V/10mV = 500. Gain (dB) = 20 log₁₀(500) ≈ 54 dB.
An ideal op-amp has zero input offset voltage, zero input bias current, infinite gain, infinite input impedance, and zero output impedance.
Non-inverting amplifier uses negative feedback from output to inverting input, which reduces gain but improves linearity, bandwidth, and input impedance.
Hartley oscillator uses two inductors and one capacitor in the tank circuit. Frequency f = 1/(2π√L_eq×C) where L_eq is equivalent inductance.
For inverting amplifier, Gain = -Rf/Rin = -100k/10k = -10. The negative sign indicates 180° phase shift.
Non-inverting amplifier gain Av = 1 + (RF/Ri). With RF=0 (short circuit), gain=1 (unity gain buffer). As RF increases, gain increases.
Ideal op-amp has: infinite input impedance (Zin→∞), infinite open-loop gain (A→∞), zero output impedance (Zout→0), infinite bandwidth (BW→∞).
Common emitter provides both voltage and current gain with gain values typically 100-1000. CB provides only current gain, CC provides only voltage gain close to 1.
