: Ensure the semiconductor material is the same (Silicon or Germanium). Silicon transistors usually have a 0.6V–0.7V forward bias drop, while Germanium is 0.2V–0.3V . Voltage Ratings ( VCEOcap V sub cap C cap E cap O end-sub VDScap V sub cap D cap S end-sub
| Original | Type | Vdss (V) | Id (A) | Rds(on) (Ω) | Equivalent Options | | :--- | :--- | :--- | :--- | :--- | :--- | | IRF540 | N-MOSFET | 100 | 28 | 0.077 | IRF540N, NTE2397, STP40NF10 | all type transistor equivalent pdf
) : The transition frequency should meet or slightly exceed the original. Avoid significantly higher fTf sub cap T in some circuits as it can cause unwanted oscillations . : Ensure the semiconductor material is the same
): For BJTs, the current gain should be roughly the same as the original to maintain circuit performance. Avoid significantly higher fTf sub cap T in