i will explain something about transistor..
what is transisor?
-> A transistor is a device that regulates current or voltage flow.
-> The transistor is like an electronic switch. It can turn a current on and off.
-> It has three pins: Base (b), collector (c) and emitter (e).
There are two main types of transistor:
- bipolar transistors
- field effect transistors
The schematic symbol for the NPN looks like this:
consider the following image..
-> If a current flow from base to emitter means it allow large current flow from collector to emitter..
Let’s look at an example:
-> In the example above you can see how transistors work. A 9V battery connects to an LED and a resistor. But it connects through the transistor. This means that no current will flow in that part of the circuit until the transistor turns ON.
-> To turn the transistor ON you need to apply 0.7V from base to emitter of the transistor. Imagine you have a small 0.7V battery. (In a practical circuit you would use resistors to get the correct voltage from whatever voltage source you have)
-> When you apply the 0.7V battery from base to emitter, the transistor turns ON. This allows current to flow from the collector to the emitter. And thereby turning the LED ON!