| Manufacturer | Part Number | Description |
|---|---|---|
STMicroelectronics
| MJE521 | SILICON NPN TRANSISTOR |
| MJE521 | Silicon NPN Power Transistor | |
| MJE521G | Plastic Medium-Power NPN Silicon Transistor | |
| MJE521 | POWER TRANSISTOR | |
Motorola Semiconductor (now NXP Semiconductors)
| MJE521 | 4 AMPERE POWER TRANSISTOR |
| MJE521 | Plastic Medium-Power NPN Silicon Transistor |