Microwave Transistor vs. TED: Key Differences

Microwave electronic devices are essential components in high-frequency systems such as wireless communication, radar, satellite communication, and microwave instrumentation. Among these devices, microwave transistors and Transfer Electron Devices (TEDs) are widely used for microwave signal amplification and generation. Although both operate at microwave frequencies, they differ in their operating principles, construction, applications, and performance characteristics.

Microwave Transistor

• Microwave transistor devices include BJTs, FETs, HBTs, and tunnel diodes designed for microwave frequencies.
• Charge Carriers: Both electrons and holes are involved in the electrical transport within the device.
• Structure: Transistors incorporate junctions or gates to control current flow.
• Materials: Commonly fabricated using elemental semiconductors like Germanium (Ge) and Silicon (Si).
• Electron Energy: Operates with “warm” electrons, implying lower energy levels.
• Applications:
  • S and L band RF transmitters.
  • L and S band high-speed switching devices.
  • Microwave amplification and oscillation circuits.
  • Memory and switching devices.
• Advantages:
  • Low cost.
  • Low power supply requirements.
  • Small size.

TED (Transfer Electronic Device)

• TEDs encompass Gunn diodes, LSA diodes, and InP diodes.
• Electron Transfer: The fundamental principle involves the transfer of electrons from a lower conduction valley to an upper satellite valley within the semiconductor’s energy band structure.
• Structure: TEDs are bulk devices, meaning they lack junctions or gates found in transistors.
• Materials: Typically made from compound semiconductors like Gallium Arsenide (GaAs) and Indium Phosphide (InP).
• Electron Energy: Operates with “hot” electrons, indicating higher energy levels.
• Applications:
  • L, S, C, and X band amplifiers and oscillators.
  • RF transmitters.
  • Radar systems.
• Advantages:
  • Low noise.
  • High gain.
  • Low power consumption.
  • High reliability.
  • Lighter weight.

Difference between Microwave transistor and TED

Feature	Microwave Transistor	Transfer Electron Device (TED)
Definition	Three terminal semiconductor device used mainly for microwave amplification and switching	Two terminal semiconductor device used mainly for microwave oscillation
Number of Terminals	Three (e.g., source, gate, drain or emitter, base, collector)	Two (anode and cathode/ohmic contacts)
Operating Principle	Controls carrier flow using an electric field or current to provide gain	Operates using the transferred electron (Gunn) effect and negative differential resistance
PN Junction	Present in some types (e.g., BJTs); FETs use a gate structure	No PN junction
Primary Function	Amplification, switching, oscillation, mixing	Microwave signal generation (oscillation)
Signal Gain	Provides amplification	Does not provide amplification
Frequency Capability	Microwave to millimeter wave frequencies, depending on technology	Primarily microwave frequencies
Bias Requirement	Requires controlled bias for amplification	Requires a DC bias above the threshold electric field
Output Power	Moderate to high, depending on device technology	Generally moderate and application dependent
Noise Performance	Low (especially HEMTs and modern FETs)	Higher phase noise than many transistor oscillators
Circuit Complexity	More complex due to matching and bias networks	Simpler oscillator circuits
Common Semiconductor Materials	Si, GaAs, GaN, InP	GaAs, InP
Typical Applications	5G communication, satellite links, radar receivers, RF amplifiers, MMICs	Gunn oscillators, speed radar, automatic door sensors, microwave sources

Summary

Microwave transistors and Transfer Electron Devices are both important microwave semiconductor components, but they serve different purposes. Microwave transistors are versatile three terminal devices capable of amplification, switching, and oscillation, making them essential in modern communication systems.

In contrast, Transfer Electron Devices are two terminal negative-resistance devices that generate microwave oscillations through the transferred electron effect. The selection of either device depends on whether the application requires signal amplification or microwave signal generation.