The BC558 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.
The PCF8591 is a monolithic single supply low power 8-bit CMOS data acquisition device. PCF8591 has four analog inputs, one analog output and a serial I2C bus interface.
This STP80PF55 P-Channel 55V - 0.016Ω - 80A P-Channel Power MOSFET - TO-220. This Power MOSFET is the least development of STMicroelectronics unique “Single feature size™” strip-based process.
The SI-9945DY, SI9945, 9945 is a N-Channel Dual MOSFET 60V 4.3A 2W 58mohm 10V Enhancement Mode MOSFETs are produced using advance process that has been especially tailored to minimize on-state resistance and yet maintain superior switching performance.