Question 1.12: Objective: Determine diode voltages. The reverse saturation ...

Microelectronics Circuit Analysis and Design

Objective: Determine diode voltages. The reverse saturation currents of a pn junction diode and a Schottky diode are $I_{S} = 10^{−12} A$ and $10^{−8} A$ , respectively. Determine the forward-bias voltages required to produce 1 mA in each diode

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The diode current-voltage relationship is given by

I_{D} = I_{S} e^{V_{D}/V_{T}}

Solving for the diode voltage, we obtain

V_{D} = V_{T} \ln \left(\frac{I_D}{I_{S}} \right)

We then find, for the pn junction diode

V_{D} = (0.026) \ln \left( \frac{1 \times 10^{-3}}{10^{-12}} \right) = 0.539  V

and, for the Schottky diode

V_{D} = (0.026) \ln \left( \frac{1 \times 10^{-3}}{10^{-8}} \right) = 0.299  V

Comment: Since the reverse-saturation current for the Schottky diode is relatively large, less voltage across this diode is required to produce a given current compared to the pn junction diode

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