# Basic Electronics: Transistor confusion

• thegreengineer
In summary, the textbook says current flows from the emitter to the base and then to the collector, but the drawing seems to say that it should go in the opposite direction. The text also says that two resistors are used to prevent the transistor from overheating, but the current is flowing first to the transistor and then to the resistor, which is not what the drawing says.
thegreengineer
So, recently I started learning about electronic components and then I started learning about semiconductors. The one which I've been having some real trouble to understand its function is the transistor.
So I bought an electronics textbook called El ABC de La Electrónica (The ABC of Electronics in Spanish) to check how it actually works; as well to learn more about electronics.
My doubt focuses on a couple of drawings of how a NPN transistor (BJT type) works:

This drawing basically represents the how electric current would travel across the transistor if this were connected to two 10 V batteries, however I got confused on this because how does current flow from the emitter (emisor) to the base and at the same time how does it flow from the emitter to the collector? Also the text says that two resistors were used to prevent the transistor from overheating but the current is flowing first to the transistor and then to the resistor according to what the drawing says; or should it be in the other way otherwise? I need to solve this doubt because I really want to learn electronics and if I don't learn how to properly use the transistor then I won't be able to make proper circuits.

Sorry for the Spanish text, but I'm from Mexico and really this is the closest thing I've seen that helps me even that I still don't solve entirely my doubts.

Thanks.

MarcusAu314 said:
how does current flow from the emitter (emisor) to the base and at the same time how does it flow from the emitter to the collector?
Where do you see a problem here?
MarcusAu314 said:
Also the text says that two resistors were used to prevent the transistor from overheating but the current is flowing first to the transistor and then to the resistor according to what the drawing says; or should it be in the other way otherwise?
If you want to limit currents, the order does not matter. In a circle, current flow is the same everywhere. In this setup, the order matters a bit because a resistor directly at the emitter would influence both current circles.

thegreengineer
thegreengineer

## 1. What is a transistor and how does it work?

A transistor is a semiconductor device that can amplify or switch electronic signals. It consists of three layers of doped material, known as the emitter, base, and collector. By applying a small current to the base, a much larger current can be controlled between the emitter and collector, allowing for signal amplification.

## 2. What is the difference between NPN and PNP transistors?

NPN and PNP transistors are two types of bipolar junction transistors (BJTs). The main difference between them is the direction of the current flow. In an NPN transistor, current flows from the collector to the emitter, while in a PNP transistor, current flows from the emitter to the collector.

## 3. How do I choose the right transistor for my circuit?

There are several factors to consider when choosing a transistor for your circuit, such as the required voltage, current, and frequency of operation. You also need to consider the gain, power dissipation, and temperature range. It is best to consult a datasheet or seek advice from an experienced electronics engineer.

## 4. What is the purpose of biasing a transistor?

Biasing a transistor means applying a steady voltage or current to the base of the transistor to keep it in its active region. This allows the transistor to amplify a signal without distortion. Biasing also helps to stabilize the operating point of the transistor, ensuring that it remains in the desired mode of operation.

## 5. Can I use a transistor as a switch?

Yes, transistors can be used as switches. By controlling the current on the base of the transistor, you can turn it on or off, allowing or blocking the flow of current between the collector and emitter. This is commonly used in digital circuits to control the flow of electricity.

Replies
3
Views
1K
Replies
68
Views
4K
Replies
5
Views
3K
Replies
16
Views
5K
Replies
19
Views
2K
Replies
11
Views
2K
Replies
60
Views
13K
Replies
10
Views
1K
Replies
19
Views
5K
Replies
7
Views
2K