Understanding the Difference Between Field-Effect Transistors (FETs) and Bipolar Junction Transistors (BJTs)

Control Mechanism

• FETs: Voltage-controlled devices. The gate-source voltage (V_GS) modulates the conductivity of the channel between the drain and source. This makes them ideal for low-power, high-input-impedance applications .

• BJTs: Current-controlled devices. The base current (I_B) regulates the collector-emitter current (I_C). They require continuous base current, leading to higher power consumption .

2. Construction and Charge Carriers

• FETs: Unipolar devices. Current flows through majority carriers (electrons in N-channel, holes in P-channel). This results in lower noise and better thermal stability .

• BJTs: Bipolar devices. Current involves both majority and minority carriers (electrons and holes), making them more susceptible to thermal runaway .

3. Input Impedance

• FETs: Extremely high input impedance (10⁷–10¹⁵ Ω), minimizing signal loading. This is critical for amplifiers and sensitive circuits .

• BJTs: Lower input impedance (1–10 kΩ), requiring additional biasing resistors .

4. Applications

• FETs: Excel in high-frequency circuits, power switching (e.g., MOSFETs in inverters), and low-noise amplifiers. 佑风微’s YFW40P03DF MOSFET, for example, is optimized for automotive chargers and consumer electronics .

• BJTs: Common in audio amplifiers, oscillators, and low-power switching. 佑风微’s 2SA1015 PNP transistor is widely used in signal processing and control circuits .

5. Advantages

• FETs: Low power consumption, fast switching, and radiation resistance .

• BJTs: High current gain (β) and linear characteristics for analog amplification .