What Is a Transistor?

A transistor is a solid-state semiconductor device (including diodes, triodes, field-effect transistors, thyristors, etc., sometimes referred to as a bipolar device in particular). . As a variable current switch, a transistor can control the output current based on the input voltage. Unlike ordinary mechanical switches (such as Relays and switches), transistors use electrical signals to control their opening and closing, and the switching speed can be very fast. The switching speed in the laboratory can reach more than 100GHz.

Transistor

(Electronic component)

A transistor is a solid semiconductor device (including

Strictly speaking, transistor refers to all single elements based on semiconductor materials, including various

A transistor is a semiconductor device.

In December 1947,

1) Vacuum triode

In February 1939, Bell Labs made a great discovery, the birth of silicon p_n junctions. In 1942, a student named Seymour Benzer from a research group led by Purdue University Lark_Horovitz discovered that germanium single crystals had excellent rectification performance not found in other semiconductors. These two findings met the requirements of the U.S. government and laid the groundwork for subsequent transistor inventions. ^[2]

December 16, 1947: William Shockley, John Bardeen, and

with

Transistor, real name is

The main parameters of the transistor are current amplification factor, power dissipation, frequency characteristics, maximum collector current, maximum reverse voltage, and reverse current.

Control high power

Current power transistors can control hundreds of kilowatts of power. There are many advantages to using power transistors as switches, mainly;

(1) It is easy to shut down and requires few auxiliary components.

(2) The switch is fast and can work at a very high frequency.

(3) Available devices withstand voltage range from 100V to 700V, everything.

A few years ago, the switching capacity of transistors was less than 10kW. Currently, it can control power up to several hundred kilowatts. This is mainly due to the joint efforts of physicists, technicians and circuit designers to improve the performance of power transistors. Such as

(1) the increase of the effective chip area of the switching transistor,

(2) technical simplification,

(3) the recombination of transistors-Darlington,

(4) Advances in base drive technology for high-power switches. ,

Transistor power switch working directly on rectified 380V mains

Transistor recombination (Darlington) and paralleling are both effective ways to increase the switching capability of a transistor.

In such a high-power circuit, the main problem is wiring. Very high switching speeds can produce quite high interference voltages on very short connection lines.

High performance from simple and optimized base drivers

Today's base drive circuits not only drive power transistors, but also protect them. This is called "non-centralized protection" (as opposed to centralized protection). The functions of the integrated drive circuit include:

(1) Turn on and off the power switch;

(2) Monitor the auxiliary power voltage;

(3) Limit the maximum and minimum pulse widths;

(4) Thermal protection;

(5) Monitor the saturation voltage drop of the switch.

Earlier in 2010, Samsung announced that it had completed the development of a 30nm process 2Gb density DDR3 memory chip, and recently (July) they announced that this chip product has entered the mass production stage.

According to Intel engineers, the first 22nm process

Discriminating the type of base and tube

Select the R * 100 (or R * 1K) file of the ohm file. Use a red test lead to connect one pin and a black test lead to another pin. Two resistance values can be measured, and then use a red test lead to connect another pin. Repeat the above steps to measure another set of resistance values. This is done 3 times. Among them, a set of two resistance values are very small. The red test pen corresponding to this set of values is connected to the base electrode, and the tube is PNP type. Conversely, if a black test lead is used to connect a pin, repeat the above procedure. If both resistance values are measured, the corresponding black test lead is the base, and the tube is of NPN type.

Discrimination collector

Because when the emitter and collector of the triode are properly connected, is large (the swing of the needle is large), and is much smaller when the connection is reversed. Therefore, suppose a collector is connected with an ohmic range (for NPN type, the emitter is connected to the black test lead, and the collector is connected to the red test lead). During the measurement, hold the base and the hypothesized collector with your hands. The two poles cannot be in contact. If the pointer swings large and the pointer swings after the poles are reversed, the assumption is correct, and the collector and emitter are determined.

Estimation of current amplification factor

Select R * 100 (or R * 1K) in ohm range. For NPN tube, the red test lead is connected to the emitter and the black test lead is connected to the collector. When measuring, just hold the base and the collector with your hands (the two poles cannot be touched) ), And the size of the small pointer swing in both cases, the larger the swing, the higher the value.

The transistors in the circuit are mainly

1. Detection of ordinary Darlington tube

The internal Darlington tube is composed of two or more transistor collectors connected together, and a plurality of emitter junctions are included between the base b and the emitter e. When testing, you can use the multimeter R × 1 k or R × 10 k to measure.

Measure the forward and reverse resistance values between the electrodes of the Darlington tube. Normally, the forward resistance between collector c and base b (when measuring NPN tube, black test lead is connected to base b; when measuring PNP tube, black test lead is connected to collector c). The forward resistance is similar, ranging from 3 to 10 k, and the reverse resistance is infinite. The forward resistance between the emitter e and the base b (the black test lead is connected to the base b when measuring NPN tubes; the black test lead is connected to the emitter e when measuring PNP tubes) is between the collector c and the base b The forward resistance value is 2 to 3 times, and the reverse resistance value is infinite. The positive and negative resistance values between the collector c and the emitter e should be close to infinity. If the positive and reverse resistance values between the c and e poles of the Darlington tube or the positive and reverse resistance values between the b, e, b, and c poles are close to 0, it means that the tube has broken down. damage. If the forward and reverse resistance values between the b, e, and b and c poles of the Darlington tube are measured to be infinite, it indicates that the tube has been damaged by an open circuit.

2. Detection of high power Darlington tube

The high-power Darlington has added a protection circuit composed of a freewheeling diode and a bleeder resistor on the basis of the ordinary Darlington tube. Pay attention to the influence of these components on the measurement data when measuring.

Use the multimeter R × 1 k or R × 10 k range to measure the forward and reverse resistance values of the Darlington collector junction (between collector c and base b). Under normal conditions, the forward resistance value (when the base of the NPN tube is connected to a black test lead) should be small, ranging from 1 to 10 k, and the reverse resistance value should be close to infinity. If the positive and reverse resistance values of the collector junction are measured to be very small or infinite, it means that the tube has broken down and is short-circuited or open-circuit damaged.

Use the multimeter R × 100 scale to measure the forward and reverse resistance values between the Darlington emitter e and the base b. Normal values are several hundred ohms to several thousand ohms (the specific data is based on The resistance values of the two resistors are different. For example: BU932R, MJ10025 and other models of high-power Darlington tubes, the positive and reverse resistance values between the b and e poles are about 600 ), if measured The resistance value is 0 or infinite, which means that the tube under test is damaged.

Using a multimeter R × l k or R × 10 k, measure the forward and reverse resistance values between the Darlington emitter e and the collector c. Normally, the forward resistance value (when measuring NPN tube, black test lead is connected to emitter e, red test lead is connected to collector c; when measuring PNP tube, black test lead is connected to collector c, red test lead is connected to emitter e) should be 5 15 k (7 k for BU932R), the reverse resistance value should be infinite, otherwise the c and e poles (or diodes) of the tube will break down or be damaged by open circuit. ^[3]

Beijing, May 26, 2010 According to a report by the physicist organization network, American and Australian scientists have successfully produced the world's smallest transistor-a "quantum dot" composed of 7 atoms on the surface of a single crystal silicon, marking We have taken an important step towards a new era of computing power.

Intel Corporation announced on May 4, 2011 that it has developed a three-dimensional structure transistor that can be put into mass production.

Both professional radio maintenance personnel. As an amateur radio enthusiast, transistor replacement problems are encountered in work. If you master the principle of transistor replacement, you can often do more with less and improve maintenance efficiency. The principle of transistor replacement can be summarized into three principles: the same type, similar characteristics, and similar shapes.

First, the same type

1. The materials are the same. That is, a germanium tube replaces a germanium tube, and a silicon tube replaces a silicon tube.

2. Same polarity. That is, the npn-type tube replaces the npn-type tube, and the pnp-type tube replaces the pnp-type tube.

Similar characteristics

The transistor used for replacement should have similar characteristics to the original transistor, and their main parameter values and characteristic curves should be similar. There are nearly 20 main parameters of the transistor. It is required that all of these parameters are similar, which is not only difficult but also unnecessary. In general, as long as the following main parameters are similar, the replacement requirements can be met.

1. DC Dissipation Power of Collector Board (pcm)

Generally requires a transistor with pcm equal to or larger than the original tube for replacement. However, after calculation or testing, if the actual DC dissipated power of the original transistor in the entire circuit is much smaller than its pcm, it can be replaced with a transistor with a smaller pcm.

2. Maximum allowable DC current of collector (icm)

It is generally required to replace the transistor with an IC that is equal to or larger than the original tube.

3 Breakdown voltage

The transistor used for replacement must be able to safely withstand the highest working voltage in the whole machine;

Source: Transmission and Distribution Equipment Network

4 Frequency characteristics

The transistor frequency characteristic parameters are commonly used in the following two:

(1) Characteristic frequency ft: It refers to the frequency at which the transistor has a common emitter current amplification factor when the test frequency is sufficiently high.

(2) Cut-off frequency fb:

When replacing the transistor, ft and fb are mainly considered. Generally required for the transistor used for replacement, its ft and fb should not be less than the corresponding ft and fb of the original transistor.

5. Other parameters

In addition to the above main parameters, for some special transistors, the following parameters should be considered when replacing:

(1) For low-noise transistors, transistors with smaller or equal noise figures should be used during replacement.

(2) For transistors with automatic gain control performance, transistors with the same automatic gain control characteristics should be used when replacing.

(3) For the switching tube, its switching parameters must also be considered during replacement.

Third, the appearance is similar

Low-power transistors are generally similar in appearance, as long as the lead wires of each electrode are clearly marked, and the lead wires are arranged in the same order as the tubes to be replaced, they can be replaced. The shapes of high-power transistors are quite different. When replacing, you should choose transistors with similar shapes and the same size to install and maintain normal heat dissipation conditions.