Product Overview
Silicon PNP General-Purpose Amplifier and Switch, TO-92, 40 V 200 mA
Condition
Unused new old stock (NOS). Sold each.
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Product Overview
National Semiconductor 2N3905, a silicon PNP bipolar junction transistor for small-signal amplifier and switching work. It is the lower-gain grade of the JEDEC pair it forms with the 2N3906.
Key Features
- Polarity: PNP, silicon
- Collector-base voltage (VCBO): 40 V
- Collector-emitter voltage (VCEO): 40 V
- Emitter-base voltage (VEBO): 5.0 V
- Collector current (IC): 200 mA
- Power dissipation (PD): 625 mW
- DC current gain (hFE): 50 to 150 at IC 10 mA
- Transition frequency (fT): 200 MHz minimum
- Package: TO-92, three leads
Applications
- Replacing a 2N3905 on a vintage audio, instrument or control board with the same gain grade the circuit was built around
- High-side switching of an indicator LED or small relay coil drawing under 200 mA
- The PNP half of a complementary push-pull or current-mirror stage paired with an NPN small-signal transistor
- Breadboard work learning PNP biasing, where the base is pulled below the emitter to turn it on
Frequently Asked Questions
Is the 2N3905 PNP or NPN?
PNP. An N-type base sits between a P-type emitter and collector, so the transistor conducts when the base is pulled below the emitter.
How does the 2N3905 differ from the 2N3906?
Gain grade. The 2N3905 is specified at hFE 50 to 150 at 10 mA collector current; the 2N3906 is the higher-gain grade at 100 to 300. A circuit designed around the 2N3905 expects the lower figure.
How much load can a 2N3905 switch?
It blocks up to 40 V collector to emitter when off and passes up to 200 mA when on. A linear stage cannot hold both at once: 40 V at 200 mA is 8 W, and the body dissipates 625 mW at most.
Beside the 2N3906 it is the modest-gain sibling, the grade a designer writes down when more gain is not the goal. Restoring an old board with the same grade keeps the repair faithful to the drawing.
