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#diodes

3 public questions tagged with this topic.

In a full-wave rectifier, the number of diodes typically used with a centre-tap transformer is:

**Capacitor filter** purpose to reduce ripple, capacitor charges to peak during diode conduction and discharges through load during non-conduction, time constant τ = R C, larger RC less ripple, ripple reduced by using capacitor or LC filter, output of half-wave without filter is pulsating half sinusoids, full-wave without filter is two half sinusoids per cycle. A full-wave rectifier with a centre-tap transformer uses two diodes, each conducting during alternate half-cycles, to rectify both positive and negative halves of the AC input. Substituting values gives 2, which matches expected behavio

Ref: NCERT > Physics Book > Electronic Devices > Rectifiers, Filters and Applications

The reverse saturation current in a diode is:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. The reverse saturation current is nearly constant with voltage (until breakdown), determined by the minority carrier concentration, not the applied reverse voltage magnitude. Substituting

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

The reverse bias resistance of a p-n junction diode is typically:

In reverse bias, the diode allows only a small reverse saturation current ( μ A ), resulting in a very high resistance compared to the low resistance in forward bias.

Ref: NCERT Physics Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII, continuing as per NCERT advisory for 2026-27), Chapter: Semiconductor Electronics (Latest NCERT 2026-27), Topic: p-n junction diode, reverse bias high resistance, small saturation curren