By applying a control voltage to the second gate (Gate 2), you can vary the gain of the signal passing through the first gate (Gate 1). This is essential for stabilizing radio reception under varying signal strengths.
Standard range (e.g., up to 125°C or higher for metal cans) Feature Look-In: The Dual-Gate Advantage The defining characteristic of the 3SK41 is its
When viewing the transistor from below (with the pins pointing toward you and the tab oriented correctly):
), leading to better stability in high-gain amplifier stages compared to single-gate MOSFETs. Common Applications RF Amplifiers:
Front-end stages for TV and radio receivers to amplify weak signals with low noise. VHF/UHF Tuners:
| Part Number | Compatibility Notes | Availability | | :--- | :--- | :--- | | | Nearly identical pinout (SOT-103). Superior noise figure (2dB). Drop-in with adapter. | Scarce | | BF998 | Surface mount (SOT-143). Higher transconductance. Requires a breakout board. | Common | | 3SK74 | Direct Japanese equivalent. Same TO-72 package. Perfect for vintage restorations. | Rare | | MPF121 | American equivalent, but higher capacitance. Not ideal above 150 MHz. | Obsolete | | Dual-gate 40673 | Metal can. Higher VDS tolerance but lower gain. Works as a slow substitute. | Obsolete |
Since an original datasheet is hard to find, use this quick in-circuit or out-of-circuit test procedure.
