This post explains for transistor.
The Part Number is A1270, 2SA1270.
The function of this semiconductor is PNP Silicon Epitaxial Planar Transistor.
The package is TO-92 Type.
Preview images :
The A1270 is PNP Silicon Epitaxial Planar Transistor for switching and general purpose applications.
The transistor is subdivided into two groups O and Y according to its DC current gain. On special request, these transistors can be manufactured in different pin configurations. TO-92 Plastic Package Weight approx. 0.19g.
A PNP transistor is a type of bipolar junction transistor (BJT) with a different structure and polarity compared to an NPN transistor.
Here are characteristics of PNP transistors:
1. Structure: A PNP transistor has a sandwich-like structure, consisting of a thin N-type layer (base) sandwiched between two P-type layers (emitter and collector).
2. Polarity: In a PNP transistor, the majority charge carriers are holes, which flow from the emitter to the collector. The emitter is negative relative to the base, and the collector is positive relative to the base.
3. Current flow: When a small current is applied to the base terminal, it allows a much larger current to flow from the emitter to the collector. This is called amplification or gain, and it makes the PNP transistor useful as an electronic switch or amplifier.
4. Voltage levels: The voltage levels in a PNP transistor are opposite to those in an NPN transistor. In a NPN transistor, the base-emitter junction is forward-biased and the collector-base junction is reverse-biased.
5. Biasing: PNP transistors are biased in the opposite direction to NPN transistors. To turn on a PNP transistor, the base must be more negative than the emitter, and to turn it off, the base must be more positive than the emitter.