Schottky Diode
Understanding Schottky Diodes
Schottky diodes are the workhorse nonlinear element for RF frequency conversion and detection. Their ultra-fast switching enables mixing and detection well into the terahertz range, far beyond what PN junctions can achieve.
Schottky Diode Properties
- Forward voltage: 0.15-0.45V (lower than PN junction's 0.6V).
- Switching speed: Picoseconds. No minority carrier storage time.
- Frequency range: DC to 1+ THz depending on junction geometry.
- Applications: Mixers, detectors, frequency multipliers, switched attenuators.
Schottky vs PN Junction
- Speed: Schottky is 100-1000x faster (no minority carrier storage).
- Forward voltage: Schottky 0.3V vs PN 0.6V. Better detection sensitivity.
- Leakage: Schottky has higher reverse leakage. Less suitable for power rectification.
Frequently Asked Questions
What is a Schottky diode?
A Schottky diode uses a metal-semiconductor junction for ultra-fast switching (picoseconds). It is the dominant diode for RF mixers and detectors from DC to 1 THz. Its low forward voltage (0.3V) provides better detection sensitivity than PN diodes.
Why are Schottky diodes used in mixers?
Mixing requires a fast-switching nonlinear element. Schottky diodes switch in picoseconds (no minority carrier storage), enabling frequency conversion well into mmWave and sub-THz ranges. GaAs Schottky diodes work above 100 GHz.
What is a zero-bias Schottky detector?
A zero-bias Schottky detector operates without any DC bias, simplifying the circuit. It detects RF power by rectifying the RF signal through the diode's nonlinear I-V characteristic. Used in power meters, RFID tags, and simple receivers.