gen-define-a-diode-s-i-v-curve-and-give-one-short-worked-example-269b

Define a diode's I-V curve and give one short worked example.

# Diode I-V Curve ## Definition The **current-voltage (I-V) characteristic** of a diode describes the relationship between the current flowing through it and the voltage across it: $$I = I_S \left(e^{\frac{V}{nV_T}} - 1\right)$$ Where: - **I** = diode current - **I_S** = reverse saturation current (typically 10⁻¹² to 10⁻¹⁵ A) - **V** = voltage across the diode - **n** = ideality factor (1 to 2, typically ~1 for silicon) - **V_T** = thermal voltage = kT/q ≈ 26 mV at room temperature (300K) **Key regions:** - **Forward bias (V > 0)**: Current increases exponentially; diode conducts (typically V > 0.7V for silicon) - **Reverse bias (V < 0)**: Tiny leakage current ≈ -I_S; diode blocks current --- ## Worked Example **Problem:** A silicon diode has I_S = 10⁻¹³ A and n = 1. Find the current when V = 0.7 V at room temperature. **Solution:** Given: V_T = 26 mV = 0.026 V $$I = 10^{-13} \left(e^{\frac{0.7}{1 \times 0.026}} - 1\right)$$ $$I = 10^{-13} \left(e^{26.92} - 1\right)$$ $$I = 10^{-13} \times (4.74 \times 10^{11}) \approx \boxed{47.4 \text{ mA}}$$ The diode conducts significant current in forward bias.