Beginner
PN Junction Diode
A one-way valve for electric current.
STEP 1 · CONCEPT
Joining p-type and n-type silicon forms a depletion region that blocks current until enough forward voltage is applied.
STEP 2 · BIAS
Forward bias (~0.7 V for silicon) lets current flow. Reverse bias blocks it, except a tiny leakage.
STEP 3 · USE
Rectifiers convert AC to DC using diodes.
WORKED EXAMPLE
A 5 V source, silicon diode and 430 Ω resistor in series: I = (5 − 0.7)/430 = 10 mA.
Formulas
Diode current
I = I_s (e^(V/ηV_T) − 1)
V_T ≈ 26 mV at room temperature
Half-wave avg
V_dc = V_m / π
Practice questions
Q1.Cut-in voltage of a silicon diode is about…
PN Junction Diode · Easy
Q2.In reverse bias, the depletion region…
PN Junction Diode · Medium
Q3.Average output of a half-wave rectifier with peak Vm?
PN Junction Diode · Medium