Schottky and Varactor Diodes

Schottky diode

• Metal-semiconductor junction
• Lower $V_F$ than PN diode
• Higher reverse (leakage current)
• Use this if we want something that turns on quickly and don’t care about leakage.

Varactor Diodes:

• Depletion layer is like a parallel-plate capacitor
• Varactor uses this effect to act as a voltage-controlled capacitor
• Usually operated in reverse bias

• Recall parallel plate cap from high school:

$$C=\frac{ϵA}{d}$$

where $d$ is a depletion region, width changes with $V_R$ reverse bias