Transistor source, and the difference between NPN and PNP

btty038

Transistor source, and the difference between NPN and PNP [Copy link]

I have shared with you knowledge about transistors before, and today I will continue to share related content with you.

1. Review of History

Before sharing the transistor NPN and PNP, let me share with you some basic knowledge.

1. Electron tube

Before the advent of transistors, there was a device that functioned similarly to a transistor, called a vacuum tube.

In 1904, the world's first electronic diode was born under the hands of British physicist Fleming.

The electron tube is one of the earliest electrical signal amplifier devices.

A cathode electron emission part enclosed in a glass container (usually a glass tube), a control grid, an accelerating grid, and an anode (screen) lead are welded to the tube base. An electric field is used to inject an electronic modulation signal into the control grid in a vacuum, and different parameter signal data are obtained at the anode after signal amplification or feedback oscillation.

Electron tubes were used in early electronic products such as televisions, radio amplifiers, etc. In recent years, they have gradually been replaced by amplifiers and integrated circuits made of semiconductor materials. However, in some high-fidelity audio equipment, low-noise, high-stability electron tubes are still used as audio power amplifiers.

Advantages and disadvantages of electron tubes:

Disadvantages: large size, high power consumption, severe heat generation, short life, low power efficiency, fragile structure and requirement of high voltage power supply.

Advantages: strong load capacity, better linear performance than transistors, high operating frequency, and better than transistors in the high-frequency and high-power field.

Electrons are very large (relative to transistors). The world's first computer in 1946 was built using 1.8W electron tubes, occupied an area of 150 square meters, weighed 30 tons, and consumed about 150 kilowatts of power.

2. Transistor

Because vacuum tubes have many shortcomings, humans invented transistors, which are more advanced than vacuum tubes.

A transistor is a solid semiconductor device , including diodes, triodes, field effect transistors, thyristors, etc. It has multiple functions such as detection, rectification, amplification, switching, voltage regulation, and signal modulation.

December 16, 1947: William Shockley, John Barton, and Walter Brattain successfully create the first transistor at Bell Labs.

The first transistor model:

As a variable current switch , a transistor can control the output current based on the input voltage. Unlike ordinary mechanical switches, transistors use electrical signals to control their own opening and closing, and the switching speed can be very fast, reaching more than 100GHz in the laboratory.

I also shared a video with you before: How transistors work

The video above shows the basic working principle of transistors.

3. Transistor

Triode, whose full name should be semiconductor triode, is also called bipolar transistor and crystal triode . It is a type of transistor.

A transistor is a semiconductor device that controls current. Its function is to amplify weak signals into electrical signals with larger amplitudes, and it is also used as a contactless switch.

The transistor is one of the basic semiconductor components, with the function of current amplification, and is the core component of the electronic circuit. The transistor is made by making two PN junctions very close to each other on a semiconductor substrate. The two PN junctions divide the entire semiconductor into three parts. The middle part is the base area, and the two sides are the emitter area and the collector area. There are two arrangements: PNP and NPN .

2. Difference between NPN and PNP

N： Negative, negative electrode

P： Positive

Crystal triodes are divided into two types according to materials: germanium tubes and silicon tubes. Each type has two structural forms, NPN and PNP, but the most commonly used are silicon NPN and germanium PNP triodes.

1. Different definitions

NPN transistor: It is composed of two N-type and one P-type semiconductors, with the P-type semiconductor in the middle and two N-type semiconductors on both sides. The transistor is the most important device in electronic circuits, and its main functions are current amplification and switching.

PNP transistor: A transistor composed of two P-type semiconductors with one N-type semiconductor in between, so it is called a PNP transistor. It can also be described as a transistor in which current flows from the emitter E.

2. Current control is different

NPN: Use the current from B to E (IB) to control the current from C to E (IC). The potential of the E pole is the lowest, and the potential of the C pole is usually the highest during normal amplification, that is, VC > VB > VE

PNP: Use the current from E to B (IB) to control the current from E to C (IC). The potential of the E pole is the highest, and the potential of the C pole is usually the lowest during normal amplification, that is, VC < VB < VE

3. Different output status

PNP and NPN sensors actually use the saturation and cutoff of transistors to output two states, which are switch sensors. However, the output signals are completely opposite, that is, high level and low level. NPN output is low level 0, and PNP output is high level 1.

Today I will review the knowledge of triodes. If you still don't understand, please go back to school and ask your teacher to teach you again.

btty038

gk18965 posted on 2019-10-22 18:21 6666, well written, I learned a lot after reading it

It's not written by me, I'm just a porter: handshake

led2015

At our level, we still like those large-scale experiments. After completing a project, we are dumbfounded.

btty038

led2015 posted on 2019-10-22 23:28 At our level, we still like those large-scale experiments. After completing a project, people are dumbfounded

Especially when it comes to high power and high frequency, even if it's wrong, it's not necessarily high frequency. Anything bigger can really make people stupid. I really experienced this. A whole team was dumbfounded.