BC557 is a PNP transistor hence the collector and emitter will be closed (Forward biased) when the base pin is held at ground and will be opened (Reverse biased) when a signal is provided to base pin. This is where a PNP transistor differs from a NPN transistor.
BC557 Transistor Pinout Configuration
|Pin Number||Pin Name||Description|
|1||Collector||Current flows in through collector|
|2||Base||Controls the biasing of transistor|
|3||Emitter||Current Drains out through emitter|
BC557 Transistor Features
Note: Complete Technical Details can be found at the BC557 datasheet given at the download menu of this page.