How do I select a GaN HEMT for a high power microwave amplifier application?
GaN HEMT Selection
GaN HEMT selection begins with the target output power and frequency. The required gate periphery is P_target / P_density, where P_density is typically 5-8 W/mm at sub-6 GHz and 3-5 W/mm at mmWave frequencies. A 50W C-band PA requires 6-10 mm of gate periphery, which is available in a single die from most GaN foundries.
| Parameter | LNA | Driver | Power Amplifier |
|---|---|---|---|
| Noise Figure | 0.3-2.0 dB | 3-8 dB | 5-15 dB (not specified) |
| Gain | 10-25 dB | 10-20 dB | 8-15 dB |
| P1dB | -10 to +10 dBm | +15 to +25 dBm | +30 to +50 dBm |
| OIP3 | +5 to +25 dBm | +25 to +40 dBm | +40 to +55 dBm |
| DC Power | 10-100 mW | 0.5-5 W | 5-500 W |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
- Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture
Frequently Asked Questions
28V or 48V supply?
28V is the industry standard for defense and most base station applications, with the widest selection of devices. 48V provides higher Ropt (easier matching, wider bandwidth) and is gaining adoption in massive MIMO base stations. 48V devices require higher breakdown voltage (> 100V) and careful supply regulation.
What about GaN-on-SiC vs GaN-on-Si?
GaN-on-SiC provides 3-4× better thermal conductivity, enabling higher power density and higher operating temperature. GaN-on-Si is cheaper but thermally limited. For power levels above 10W, GaN-on-SiC is strongly preferred. GaN-on-Si targets sub-10W applications where cost is the primary driver.
How do I evaluate reliability?
Request the manufacturer's reliability qualification report including: accelerated life test (ALT) data at elevated junction temperature, MTTF extrapolation to operating temperature using the Arrhenius model, and failure mode analysis. Look for MTTF > 10^6 hours at 200°C junction temperature for telecom applications.