If you’re looking for a reliable high-voltage NPN transistor for demanding projects, the Chanzon MJE340 is a strong contender. With VCBO and VCEO ratings up to 300V and a power dissipation of 20W, this TO-126 BJT handles both voltage and heat efficiently. Ideal for power supplies, motor control, and audio amplification, it’s also the perfect complement to the MJE350 PNP transistor. Whether you’re prototyping or repairing, these transistors offer dependable performance at a budget-friendly price.
| ▌ PRODUCT | ▌ QUALITATIVE INFO |
 | > Model: MJE340 TO-126 > Type: High-Power NPN Bipolar Junction Transistor > Maximum VCBO: 300V > Maximum VCEO: 300V > Maximum VEBO: 3V > Maximum Collector Current (IC): 0.5A > Power Dissipation (PC): 20W > Package: Anti-Static Bag (ESD Safe) > Applications: Power Supplies, Motor Control, Amplifiers, Complement to MJE350 |
I’ve used the MJE340 in a few high-voltage amplifier builds, and what stands out is how calm it runs under stress. Even when pushing near the upper voltage limit, it maintains stability without sudden thermal spikes—though a decent heatsink is still a must. Its TO-126 package makes it easier to mount in tight spaces compared to bulkier TO-220s, yet it still dissipates heat well when paired with proper airflow.
One project where it surprised me was a vintage preamp repair—swapping in the MJE340 not only matched the original specs but actually reduced background hiss. It also pairs seamlessly with the MJE350 for complementary push-pull stages, something worth noting if you design symmetrical circuits.
FAQ
Q: Can it handle continuous operation near 300V?
A: Yes, but use a heatsink and avoid pushing it to the absolute limit for long durations.
Q: Is it a good substitute for 2SC3298?
A: In many circuits, yes, but check the pinout—some layouts differ.
Q: Does it work in switching power supplies?
A: It can, but efficiency isn’t as high as dedicated MOSFETs; it shines more in linear and moderate switching roles.
Hidden note: While the datasheet says 20W dissipation, that’s under ideal heatsinking. In a real-world enclosed chassis, expect around 12–15W before heat saturation.
I still have three from my last pack sitting in my parts drawer. Not because they’re unused, but because I keep them for those moments when a repair job needs a “drop in and forget about it” transistor.
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Beneath its standard design lies potential for something far beyond its original purpose. A kindred solution, crafted from the same hidden logic — preserved as a sealed work of mind. | |
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