3sk41 Datasheet [upd] • Tested & Trusted

Based on the technical specifications found in a typical 3SK41 Datasheet (a N-channel MOSFET used in switching applications), I have developed a specific application feature.

• VGS(th) (threshold voltage): gate voltage where channel starts to conduct (small current). Important for biasing and predicting gain.
• ID(on) or ID @ VGS: tells how much current flows at a given gate bias; for small RF dual‑gate MOSFETs, currents are small.
• RDS(on): on‑resistance when fully enhanced; affects insertion loss and dissipation.
• IGSS (gate leakage): gate stability and bias network design.
• Notes: DC values are often given at specific VDS and temperature; use the same conditions when comparing.

Dual-Gate Construction: Allows for improved AGC (Automatic Gain Control) characteristics and lower cross-modulation. Low Noise: Optimized for high-frequency sensitivity. 3sk41 datasheet

Low Noise Figure: Designed to minimize the "hiss" or thermal noise added to weak signals, making it ideal for the front-end stages of receivers. Based on the technical specifications found in a

Part 7: How to Test a 3SK41 (No Datasheet? No Problem!)

Since an original datasheet is hard to find, use this quick in-circuit or out-of-circuit test procedure. higher gain. MOSFET Dual-Gate: MFE201

4. Feature Benefits

• Inrush Current Limitation: By ramping up the duty cycle, the 3SK41 limits the initial current surge, protecting the power supply and extending the life of the motor windings or filament.
• Thermal Management: The datasheet indicates a specific $R_DS(on)$. By operating the transistor in either the fully OFF or fully ON state (PWM switching), power dissipation is kept low compared to linear regulation.
• Safety Cut-off: If the system detects an over-current event (via a shunt resistor), the microcontroller can pull the Gate of the 3SK41 low instantly, leveraging the device's fast switching speed to disconnect the load in microseconds.

• BF998 (NXP/Infineon): SOT-143 package. Superior noise figure (1.5dB at 200MHz). Pinout similar but requires careful biasing.
• 3SK299 (Renesas): The spiritual successor. Lower noise, higher gain.
• MOSFET Dual-Gate: MFE201, MFE121.

Part 5: Application Circuit – 200MHz RF Amplifier

The classic application from the 3SK41 datasheet is a cascode-like RF amplifier. Unlike a single-gate MOSFET, Gate 2 acts as a shield and a gain control.