BJT vs. FET: What's the Difference?
Edited by Aimie Carlson || By Harlon Moss || Published on August 5, 2024
BJT (Bipolar Junction Transistor) is a current-controlled device, while FET (Field Effect Transistor) is a voltage-controlled device, differing in operation and construction.
Key Differences
BJT, or Bipolar Junction Transistor, consists of a base, emitter, and collector. It operates on minority carrier injection under the influence of a forward-biased base-emitter junction. Conversely, FET, or Field Effect Transistor, includes a gate, source, and drain, with operation based on an electric field created by voltage applied to the gate, which controls the current flow.
BJT is a current-controlled device where the base-emitter current controls the collector-emitter current. FET, on the other hand, is a voltage-controlled device where the gate-source voltage controls the drain-source current. This fundamental difference in control mechanism dictates their respective applications and performance characteristics.
BJTs generally handle more power compared to FETs and are preferred in high-power applications. However, FETs offer higher efficiency, especially at lower power levels, due to their lower gate current requirements. This efficiency makes FETs more suitable for battery-powered and portable devices.
FETs typically have faster switching speeds and better high-frequency performance than BJTs. This is due to the absence of minority carrier storage in FETs, which leads to quicker response times, making them ideal for high-frequency and fast-switching applications.
BJTs are known for lower noise levels and better linearity compared to FETs, making them preferable in audio amplifiers and signal processing applications. FETs, while having higher noise levels, offer advantages in digital circuits due to their simpler gate control.
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Comparison Chart
Control Mechanism
Current-controlled
Voltage-controlled
Power Handling
Better at high power
Better at low power
Switching Speed
Slower
Faster
Frequency Response
Lower frequency performance
Higher frequency performance
Noise and Linearity
Lower noise, better linearity
Higher noise, used in digital circuits
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BJT and FET Definitions
BJT
BJT consists of three regions: emitter, base, and collector.
The base region in a BJT is typically very thin compared to the emitter and collector.
FET
FET is a field-effect transistor where output current is controlled by an electric field.
The FET in the circuit functioned as a voltage-controlled switch.
BJT
BJT operates by using both electron and hole charge carriers.
In the BJT, both electrons and holes play a crucial role in current flow.
FET
FETs are characterized by high input impedance.
The high input impedance of the FET made it ideal for the sensitive signal amplifier.
BJT
BJT can function as an amplifier, switch, or in signal modulation.
A BJT was used to switch the motor on in the circuit.
FET
FET has three terminals: source, gate, and drain.
The gate terminal of the FET is critical for controlling the current flow.
BJT
BJT is a semiconductor device for amplifying or switching electrical signals.
The audio amplifier uses a BJT to enhance the sound signal.
FET
FETs are predominantly used in digital circuits for their efficiency.
The computer's processor contains millions of FETs for rapid data processing.
BJT
BJT's conductivity is influenced by the input current.
The BJT's collector current changed significantly with a slight increase in base current.
FET
FETs operate primarily by channeling majority charge carriers.
In an n-type FET, electrons are the majority carriers responsible for current flow.
FET
(obsolete) to fetch
FET
(obsolete) a piece
FET
A piece.
FET
To fetch.
And from the other fifty soon the prisoner fet.
FET
Fetched.
FET
A transistor in which most current flows in a channel whose effective resistance can be controlled by a transverse electric field
FAQs
How does a FET work?
A FET works by using an electric field created by voltage at the gate to control current between source and drain.
Are BJTs current or voltage controlled?
BJTs are current-controlled devices.
What does FET stand for?
FET stands for Field Effect Transistor.
How does a BJT work?
A BJT works by using a small current at its base to control a larger current between collector and emitter.
In which applications are FETs commonly used?
FETs are commonly used in digital circuits, RF amplifiers, and logic gates.
What is the key advantage of FETs?
A key advantage of FETs is their high efficiency, especially in low power applications.
What does BJT stand for?
BJT stands for Bipolar Junction Transistor.
What is the key advantage of BJTs?
A key advantage of BJTs is their high power handling capability.
Are FETs current or voltage controlled?
FETs are voltage-controlled devices.
Are FETs more suitable for digital or analog circuits?
FETs are more suitable for digital circuits.
What are the main types of FETs?
The main types of FETs are Junction FET (JFET) and Metal-Oxide-Semiconductor FET (MOSFET).
Are BJTs faster or slower than FETs in switching?
BJTs are generally slower in switching compared to FETs.
Can BJTs operate with both electrons and holes?
Yes, BJTs operate with both electrons and holes as charge carriers.
What is the difference in linearity between BJTs and FETs?
BJTs generally offer better linearity compared to FETs.
What are the main types of BJTs?
The main types of BJTs are NPN and PNP transistors.
In which applications are BJTs commonly used?
BJTs are commonly used in amplifiers, switches, and power regulation.
Do FETs have high or low input impedance?
FETs have high input impedance.
Do BJTs have high or low input impedance?
BJTs have low input impedance.
Are FETs suitable for high-frequency applications?
Yes, FETs are suitable for high-frequency applications due to their fast switching.
Is the noise level higher in BJTs or FETs?
The noise level is typically higher in FETs compared to BJTs.
About Author
Written by
Harlon MossHarlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie CarlsonAimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.
