Npn and pnp transistors only turn on with a reasonably sized current. It's not like MOSFETs that can turn on even with microamps. Any NPN or PNP logic (such as

Npn and pnp transistors only turn on with a reasonably sized current. It's not like MOSFETs that can turn on even with microamps. Any NPN or PNP logic (such as TTL) in lately have current requirements.