Transistors - Bipolar (BJT)

Transistors - Bipolar (BJT) - RF

Image	Part Number	Description / PDF	Quantity	Rfq
	MRF8372GR1 Microsemi	RF TRANS NPN 16V 870MHZ 8SO	0
	2N2857UB Microsemi	RF TRANS NPN 15V 0.04A UB	0
	MRF8372R1 Microsemi	RF TRANS NPN 16V 870MHZ 8SO	0
	JANTX2N4957 Microsemi	RF TRANS PNP 30V 30MA TO72	0
	2N4957 Microsemi	RF TRANS PNP 30V 30MA TO72	0
	MRF545 Microsemi	RF TRANS PNP 70V 1.4GHZ TO39	0
	MRF553G Microsemi	RF TRNS NPN 16V 175MHZ PWR MACRO	0
	JANTXV2N2857 Microsemi	RF TRANS NPN 15V 500MHZ TO72	0
	MRF586 Microsemi	RF TRANS NPN 17V 3GHZ TO39	0
	MRF5812GR2 Microsemi	RF TRANS NPN 15V 5GHZ 8SO	0
	MRF5812G Microsemi	RF TRANS NPN 15V 5GHZ 8SO	0
	MRF8372G Microsemi	RF TRANS NPN 16V 870MHZ 8SO	0
	80262 Microsemi	RF POWER TRANSISTOR	0
	MS1649 Microsemi	RF TRANS NPN 16V 470MHZ TO39	0
	2N4427 Microsemi	RF TRANS NPN 40V 500MHZ TO39	0
	MRF586G Microsemi	RF TRANS NPN 17V 3GHZ TO39	0
	MRF4427R2 Microsemi	RF TRANS NPN 20V 8SO	0
	SD1127 Microsemi	RF TRANS NPN 18V 175MHZ TO39	0
	MRF904 Microsemi	RF TRANS NPN 15V 4GHZ TO72	0
	BFR92ALT1 Microsemi	RF TRANS 15V 4.5GHZ SOT23	0

Transistors - Bipolar (BJT) - RF

1. Overview

Radio Frequency Bipolar Junction Transistors (RF BJTs) are three-layer semiconductor devices optimized for amplification and switching in high-frequency applications (typically >100 MHz). These transistors maintain stable performance in microwave and ultra-high frequency (UHF) ranges, characterized by high current gain-bandwidth product (f_T), low noise figures, and fast switching capabilities. Their importance in modern technology spans wireless communication infrastructure, radar systems, and RF test equipment, enabling efficient signal transmission and reception in 5G networks, satellite communications, and IoT devices.

2. Main Types & Functional Classification

Type	Functional Features	Application Examples
NPN RF BJT	High electron mobility, optimized for low-noise amplification	5G base station LNAs, GPS receivers
PNP RF BJT	Complementary design for power amplification	RF power modules, automotive radar
RF Darlington Pair	High (current gain), cascaded amplification	Antenna drivers, industrial RF heaters
Heterojunction Bipolar Transistor (HBT)	Compound semiconductor materials (SiGe/GaAs), ultra-high f_T	Optical communication transceivers, mmWave systems

3. Structure & Composition

Typical RF BJT structure includes:

Material: Silicon (Si), Silicon-Germanium (SiGe), Gallium Arsenide (GaAs)
Layer Architecture: Emitter (high doping), Base (thin layer), Collector (graded doping)
Package Types: Surface-mount (SOT-89, SOT-343), Through-hole (TO-18, TO-92)
Metallization: Gold/aluminum contacts for reduced parasitic resistance

Advanced designs incorporate air-bridge structures to minimize parasitic capacitance and epitaxial layers for improved frequency response.

4. Key Technical Parameters

Parameter	Description	Typical Range
f_T (Transition Frequency)	Current gain cutoff frequency	1 GHz - 100 GHz
G_UM (Max. Available Gain)	Power gain at optimal impedance	10 dB - 30 dB
P_out (Output Power)	RMS power capability	0.1 W - 500 W
NF (Noise Figure)	Signal-to-noise degradation	0.3 dB - 5 dB
V_CE0 (Breakdown Voltage)	Collector-emitter withstand voltage	5 V - 80 V
(Junction Temperature)	Thermal stability limit	150 C - 200 C

5. Application Fields

Telecommunications: 5G massive MIMO amplifiers, fiber optic transceivers
Defense: Phased array radar systems, electronic warfare jammers
Test & Measurement: RF signal generators, spectrum analyzers
Consumer Electronics: Bluetooth LE modules, Wi-Fi 6E front-ends
Industrial: Plasma generators, RFID readers

6. Leading Manufacturers & Products

Manufacturer	Representative Product	Key Specifications
Infineon Technologies	BFP740F	f_T=50 GHz, NF=0.8 dB, P_out=18 dBm
STMicroelectronics	STAG2141	2.7 GHz dual-stage amplifier, 32 dB gain
Skyworks Solutions	ASK24011	0.05-6 GHz, 50 W GaAs power transistor
ON Semiconductor	MRF151G	125 W, 880 MHz, 40% efficiency

7. Selection Guidelines

Key considerations:

Match f_T to application frequency with 20% margin
Verify load-line requirements for power applications
Select appropriate package for thermal dissipation (e.g., TO-220 for >50 W)
Derate V_CE0 by 30% in high-temperature environments
Consider integrated solutions (RFICs) for complex impedance matching

8. Industry Trends

Future development directions:

Transition to SiGe BiCMOS technology for 100+ GHz applications
Integration with GaN-on-SiC substrates for hybrid power amplifiers
Development of 5G NR direct-conversion transmitters using HBT arrays
Advancements in wafer-level packaging (WLP) for mmWave 5G devices
Adoption of AI-driven parameter optimization in production testing