Electronic Devices, Circuits and Analog Electronics
Core concepts
Cover diode models and applications (rectifiers, clippers, clamps, Zener regulation), BJT configurations and biasing, small-signal hybrid parameters, and FET operation. Study feedback topologies (voltage-series etc.), gain and input/output impedance effects, and oscillator conditions (Barkhausen criterion). For op-amps, master ideal assumptions, inverting/non-inverting gains, integrators, differentiators, and comparators. Power amplifiers (class A, B, AB, C) and their efficiency limits are common.
Traps examiners set
- The Barkhausen criterion requires loop gain of unity and 360 degrees (or 0 degree) phase shift; oscillation needs both.
- Negative feedback reduces distortion and increases bandwidth but can cause instability if phase margin is poor.
- Class B efficiency is 78.5 percent maximum, class A is 25 percent (resistive load) or 50 percent (transformer coupled).
- Op-amp virtual ground applies only with negative feedback.
- Zener diode regulates when reverse biased beyond breakdown, not forward.
Worked rule of thumb
Inverting amplifier gain is -Rf/Rin. Example: Rf = 100 k, Rin = 10 k gives gain of -10. For a non-inverting stage, gain = 1 + Rf/Rin, so the same resistors give 11. Always check the input signal against the slew-rate and supply limits.
Practice strategy
Draw the DC bias first, then the AC small-signal model; mixing them causes most errors.