Diode I-v Characteristic

Question

In forward region, diode current increases roughly?

RankGuru · Accepted Answer

1. **Shockley Diode Equation**: The current $I$ through an ideal PN junction is given by $I = I_s (e^{V/\eta V_T} - 1)$.
2. **Variables**:
   - $V$: Applied forward voltage.
   - $I_s$: Reverse saturation current.
   - $V_T$: Thermal voltage ($\approx 26$ mV at RT).
3. **Forward Bias Behavior**: When $V$ is positive and greater than a few $V_T$, the exponential term dominates ($e^{V/\eta V_T} \gg 1$).
4. **Result**: The current follows an **exponential growth** pattern with respect to the applied voltage after crossing the 'knee' or 'cut-in' voltage.
5. **Linear Check**: Resistors follow Ohm's Law (linear); diodes are non-ohmic.

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Diode I-v Characteristic

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