| Mistake | Reality | |---------|---------| | Using ( V_CEO ) as operating voltage | It’s a maximum , stay well below (e.g., 80% max). | | Ignoring ( h_FE ) variation | Gain can drop 50% at high current. | | Using ( V_GS(th) ) as “fully on” (MOSFET) | That’s just starting to turn on. For low ( R_DS(on) ), use ( V_GS ) = 10V (or logic level). | | Forgetting heat sink needs | ( P_D ) assumes perfect heatsinking; without one, derate by ~50–80%. |
The specific parameters vary depending on whether the device is a BJT or a MOSFET. transistor datasheet