Identifying Transistor's Symbol and Layout

There are two types of standard transistors, NPN and PNP, with different circuit symbols. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon.
A transistor is a semiconductor  device used to amplify and switch  electronic  signals.
The transistor is the fundamental building  block of modern electronic devices, and its presence is ubiquitous in  modern electronic systems.
It is labeled with letter ''V'' and  then the mounting code and product code.

The leads are labeled base (B), collector (C) and emitter (E) in some  schematics while in cellphone schematics is not, just be familiar with  each leads.

What is a MOSFET?

Simple brief explanation, In mobile phones its is being used as a Switching circuit to the Camera Flash interface. It holds the large amount of voltage and then feed to camera  flash light when it is being click to take a picture. That is why the Flash of the camera give a more bright light and speed in just a matter of blink of an naked eye..
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a device used for amplifying or switching electronic signals.
A Power MOSFET is a specific type of metal oxide semiconductor field-effect transistor (MOSFET) designed to handle large amounts of power.
Its main advantages are high commutation speed and good efficiency at low voltages.



The power MOSFET is the most widely used low-voltage (i.e. less than 200 V) switch. It can be found in most power supplies, DC to DC converters and low voltage controller circuits.
There are many types Field effect transistor, this is the one is commonly used in mobile phone circuit.