Discrete semiconductors generally refer to semiconductor crystal diodes, semiconductor triodes for short, triodes, triodes and semiconductor special devices.Discrete Semiconductor Products

 

Electronic products are divided into "conductors" and "insulators" according to their electrical conductivity, semiconductors are between "conductors" and "insulators", semiconductor components are divided into "discrete" and "integrated" in the form of packaging, such as: diodes, triodes , transistors, etc.

 

A discrete semiconductor device is a semiconductor device that is designated to perform a basic electronic function and cannot be separated into individual functional components. Discrete semiconductors refer to semiconductor devices that exist independently in electronic components, usually consisting of a single transistor, diode, triode, etc. Unlike integrated circuits, discrete semiconductor devices are packaged and used individually, while integrated circuits integrate multiple devices on the same chip.

Ⅰ. Common discrete semiconductors

1. Transistor

Transistors are made of semiconductor material (usually silicon or selenide) and have three electrodes: Emitter, Base, and Collector. A transistor is a device used to amplify or switch electrical signals. According to the structure and function, it can be divided into bipolar transistors and field effect transistors.

Bipolar Transistor (BJT): Bipolar transistors are of two types: NPN type and PNP type. The NPN type consists of two N-type semiconductors sandwiching a P-type semiconductor, while the PNP type consists of two P-type semiconductors sandwiching an N-type semiconductor. Their working principle is based on controlling the base current to adjust the ratio of current amplification between collector and emitter.

Field Effect Transistor (FET): There are three main types of field effect transistors: MOSFET (Metal-Oxide Semiconductor Field Effect Transistor), JFET (Junction Field Effect Transistor), and IGBT (Insulated Gate Bipolar Transistor). FETs work by controlling the current in the channel by adjusting the gate voltage.

Transistors have both amplifying and switching properties. In amplification applications, transistors can amplify a weak input signal into a larger output signal, enabling the signal to be transmitted and processed. In switching applications, transistors can control the on and off of current, and realize digital signal processing and logic operations.

2. Thyristor

SCR, also known as triac, is a semiconductor device with control performance, which can be used for current switch control and power regulation.
The thyristor is a semiconductor device with a four-layer PNPN structure, which consists of three electrodes: Anode, Cathode and Gate. It has two working states: off state and on state.Triacs

In the off state, the SCR prevents current from flowing, acting as an open circuit breaker. When a sufficiently large forward voltage is applied between the anode and the cathode, the device is in the conduction state. At this point, the SCR will flow current until the current is cut off or a reverse voltage is applied.

Thyristors are mainly used in the control and power regulation of alternating current. It is often used in power systems to control the switching of high-power loads, such as electric motors, electric furnaces and lighting equipment. Thyristors are also used in high-power electronic equipment such as electronic converters, voltage regulators, and electric welding machines.

The conduction state of the thyristor is controlled by the trigger pulse or signal applied by the gate. When a trigger pulse is applied to the gate, the thyristor will turn from off state to on state. Once in the conduction state, the SCR will continue to conduct until the current through it drops to zero or a reverse voltage is applied.

3. Field Effect Transistor

A field effect transistor is a semiconductor device that uses an electric field to control current, and is used for current control and amplification. According to different structures and working principles, it can be divided into JFET (Junction Field Effect Transistor) and MOSFET (Metal-Oxide Semiconductor Field Effect Transistor).

JFET (Junction Field Effect Transistor): It is composed of P-type or N-type semiconductor materials, including Source, Drain and Gate. The conductivity of the JFET is achieved by controlling the reverse bias voltage at the gate-source junction.

MOSFET (Metal-Oxide Semiconductor Field Effect Transistor): MOSFET is one of the most common and widely used types of field effect transistors. It consists of metal-oxide-semiconductor (MOS) structures, including Source, Drain and Gate. By applying a voltage to the gate, the electric field between the gate and the semiconductor is controlled, thereby regulating the current flow between the drain and source. MOSFET is especially suitable for the manufacture of integrated circuits, while JFET has advantages in high frequency applications and low noise amplifiers.RF MOSFET Transistors

MOSFET can be divided into Enhancement-mode MOSFET and Depletion-mode MOSFET. An enhancement mode MOSFET is off with no gate voltage and requires a positive voltage at the gate to turn on. A depletion-mode MOSFET is turned on without a gate voltage and needs a negative voltage applied to the gate to turn it off.

Field effect transistors have the characteristics of high input resistance, low noise, low power consumption and high frequency response. They are widely used in electronic devices and systems such as amplifiers, switching circuits, analog signal processing, power control, and logic gates.

4. Diode: A diode is a device with two electrodes, which has the characteristic that current can only pass in one direction. Common diodes include rectifier diodes, Schottky diodes, etc. It has two electrodes: positive and negative. A key characteristic of a diode is its unidirectional conductivity, meaning that current can only pass in one direction. In a diode, the direction in which current can flow freely is called forward polarity, and the opposite is called reverse polarity.

A diode is forward biased when its anode is connected to a positive voltage and its cathode is connected to a negative voltage. In the forward bias state, the electrons in the P region of the diode combine with the holes in the N region to form a conductive channel, and current can flow through the diode, that is, the diode is turned on.

Conversely, a diode is reverse biased when its anode is connected to a negative voltage and the cathode is connected to a positive voltage. In the reverse bias state, the holes in the P region of the diode and the electrons in the N region are separated by the electric field effect, forming a high resistance region, and the current cannot flow through the diode, that is, the diode is cut off.

5. Transistor: A triode is an amplifying device with three electrodes (emitter, base, and collector). It is a specialized form of transistor used to amplify current and control its flow. Consists of three different types of semiconductor materials, including Emitter, Base, and Collector. The working principle of the triode is based on controlling the base current to adjust the current amplification ratio between the collector and the emitter.

Ⅱ. Working principle of discrete semiconductors

The operating principle of semiconductor discrete devices is based on the properties of semiconductor materials and electric field effects.

1. The working principle of the diode:

The diode is composed of a P-N structure, where the P-type semiconductor is Anode and the N-type semiconductor is Cathode. When a positive voltage is applied to the anode, and the cathode is grounded or a negative voltage is applied, electrons in the P-N junction region combine with holes to form a conductive channel, allowing current to pass through the diode. In the reverse polarity, that is, when the anode is negative voltage and the cathode is positive voltage, the P-N junction area forms a high impedance area, the current cannot pass through, and the diode is in a cut-off state.

2. The working principle of the transistor:

Field Effect Transistor (FET): A FET regulates current flow between source and drain based on a control gate electric field. A change in the electric field of the gate affects the conduction ability of the channel. In a MOSFET, by varying the gate voltage, the electric field between the gate and the channel is adjusted to control the drain-source current. In JFETs, the drain-source current is regulated by changing the reverse bias voltage between the gate and the channel.

Bipolar Transistor (BJT): BJT is based on P-N junction and N-P-N or P-N-P structure. When a forward current is injected at the base (electrons flow into the P region and holes flow into the N region), a conductive channel is formed allowing current to flow from the collector to the emitter. By controlling the base current, the amplification factor of the collector-emitter current can be adjusted.

3. The working principle of silicon controlled rectifier (SCR):

A thyristor is a semiconductor device with control properties. It consists of a P-N-P-N structure. When sufficient trigger pulses or signals are applied to the control electrode, the thyristor enters the conduction state. Once in the conduction state, the SCR will continue to conduct until the current through it drops to zero or a reverse voltage is applied.

 

Ⅲ. Temperature characteristics of discrete semiconductor devices

 

The temperature characterization of a discrete semiconductor device refers to the performance and behavior of the device at different temperatures. Temperature affects the electrical performance, reliability, and stability of discrete semiconductor devices.

 

1. Changes in lead characteristics: As the temperature increases, the turn-on characteristics of discrete semiconductor devices may change. For example, in a bipolar transistor (BJT), an increase in temperature can cause an increase in base current, which in turn leads to an increase in collector current. In a field-effect transistor (FET), an increase in temperature can cause a change in the relationship between gate voltage and drain current.

 

2. Reliability and lifetime: The reliability and lifetime of discrete semiconductor devices may be affected at high temperatures. High temperature will accelerate the aging and degradation process of the device, which may lead to unstable performance and shortened life of the device.

 

3. Changes in power characteristics: Temperature changes can also affect the power characteristics of discrete semiconductor devices. At high temperatures, the power loss of the device may increase, which may cause the temperature of the device to rise further, creating a positive feedback loop of thermal effects.

 

4. Impedance change: The resistance and capacitance characteristics of discrete semiconductor devices usually change with temperature. For example, in a diode, its forward resistance may decrease and its reverse resistance may increase as temperature increases.

 

Discrete semiconductor devices need to take the following measures in high temperature environment:

 

Temperature compensation: through circuit design and calibration technology, the temperature characteristics of the device are compensated to maintain the stability of its performance.

 

Temperature protection: use temperature sensors and protection circuits to monitor and limit the operating temperature of the device to prevent the temperature from exceeding the safe range.

 

Thermal Management: Use heat sinks, fans, or other cooling devices to keep the device operating within an acceptable temperature range.

 

Ⅳ. Common applications of discrete semiconductors in electronic circuits

 

1. High-frequency applications: discrete semiconductor devices are also widely used in high-frequency circuits, such as high-frequency amplifiers, radio frequency switches and tuning circuits.

 

2. Signal amplification: Discrete semiconductor devices such as bipolar transistors (BJT) and field effect transistors (FET) can be used as amplification devices to amplify weak input signals into larger output signals. This is very common in audio amplifiers, RF amplifiers and communication equipment.

 

3. Temperature sensing and measurement: Discrete semiconductor devices such as temperature sensors and thermistors can be used to measure and sense ambient temperature and convert it into electrical signals for temperature control and monitoring applications.

 

4. Switching operation: Discrete semiconductor devices such as bipolar transistors, field effect transistors, and thyristors (SCR) can be used as switches to control the current on and off in the circuit. This is used extensively in applications such as digital logic circuits, power switches, and lighting controls.

 

5. Current control: Bipolar transistors and field effect transistors can be used as current control devices to adjust the output current by controlling the input signal of the device. This is common in applications such as power management, motor drives, and current source circuits.

 

6. Rectification and voltage regulation: A diode is a common discrete semiconductor device that can be used as a rectification device to convert an AC signal into a DC signal. They can also be used in applications such as voltage clipping and circuit protection.

 

Ⅴ. Packaging Types of Discrete Semiconductors

 

1. DIP (dual in-line package): DIP is a traditional plug-in package, often used in lower power and some older devices. It has two side-by-side pinouts for integrated circuits (ICs) and some smaller discrete devices.

 

2. QFP (Quad Flat Package): QFP is a surface mount package suitable for integrated circuits and some high-density devices. It has multiple pins and is square or rectangular in shape.

 

3. TO-92: TO-92 is a small package suitable for low power applications. It has three pins and is commonly used in devices such as transistors, diodes, and temperature sensors.

 

4. TO-220: TO-220 is a common power package type for medium to high power applications. It has three pins, has good heat dissipation performance, and is often used in devices such as power transistors, thyristors (SCRs) and thyristors.

 

5. TO-126: TO-126 is a medium power package, similar to TO-220, but smaller in size. It is suitable for medium power applications and is commonly used in devices such as transistors and power diodes.

 

6. SOT-23: SOT-23 is a small surface mount package for low power applications. It usually has three pins and is commonly used in devices such as transistors, diodes, and voltage regulators.

 

7. SOT-223: SOT-223 is a surface mount package for medium power applications. It has four pins and is commonly used in devices such as voltage regulators, switching diodes, and field effect transistors.

 

Ⅵ. Advantages and disadvantages of discrete semiconductors compared with integrated circuits

 

1. Advantages:

 

Low cost: In some cases, the cost of discrete semiconductor devices may be lower. This is because the manufacturing process of discrete devices is relatively simple and does not require complex integration and packaging.

 

Flexibility: Discrete semiconductor devices can be independently selected and packaged, making them more flexible and customizable. Different types of discrete devices can be selected and combined according to specific needs to meet different application requirements.

 

High Power Handling: Some high power applications require handling of high currents and voltages, for which discrete semiconductor devices are often better suited than integrated circuits. Discrete devices can have better power handling capabilities and thermal performance.

 

2. Disadvantages:

 

Production costs: For mass-produced electronics, especially in the case of high-density and large-scale integrated circuits, discrete semiconductor devices can be more expensive to produce than integrated circuits.

 

Size and Complexity: Compared to integrated circuits, discrete semiconductor devices are typically larger and have more limited functionality per device. When complex circuits integrating multiple functions and components are required, the use of discrete components can increase the size and complexity of the circuit.

 

Heat dissipation and power consumption: Due to the typically larger size and power handling capabilities of discrete semiconductor devices, managing heat dissipation and power consumption can be more challenging. Integrated circuits optimize heat dissipation and power consumption control through on-chip wiring and packaging.

 

Complex wiring: Discrete semiconductor devices often require complex wiring connections, especially in high-density circuits. In contrast, the wiring and connections inside integrated circuits are much more compact and efficient.

 

Frequently Asked Questions

 

1. What are the development trends and future prospects of the discrete semiconductor market?

 

Technology and market trends in several areas will drive the growth of the discrete semiconductor market. This includes growing demand in areas such as electric vehicles, renewable energy, industrial automation, Internet of Things, communication equipment, consumer electronics and medical equipment. With increasing requirements for energy efficiency and environmental sustainability, the demand for high power applications is also growing.

 

Discrete semiconductor devices have better power handling capabilities to meet the demands of these high power applications. Discrete semiconductor devices have great market potential in high temperature and high voltage applications. This includes applications in areas such as aerospace, oil and gas exploration, industrial power and grids, where the demand for high reliability and high endurance devices has increased.

 

2. What is the difference between the dynamic and static characteristics of a discrete semiconductor device?

 

Static characteristics describe the performance of a device in a steady state. It is usually related to parameters such as DC current, voltage and resistance of the device. Static characteristics are obtained through static testing and measurements, which means that the device is in a steady state or resting state. Dynamic characteristics describe the performance of a device under varying conditions. It is usually related to parameters such as response speed, frequency response and time domain behavior of the device. Dynamic characteristics correspond to the behavior of a device under varying current and voltage conditions, i.e. how the device responds to rapidly changing signals.

 

3. What are the key technologies involved in the manufacturing process of discrete semiconductors?

 

Before manufacturing semiconductor devices, materials need to be cleaned and purified to remove impurities and contaminants from the surface. This can be achieved using chemical solutions, ultrapure water, and other cleaning techniques.

 

During the crystal growth process, appropriate impurities such as boron, phosphorus or arsenic are doped to alter the material's conductive properties. Doping is usually performed using techniques such as ion implantation or diffusion. By depositing metal layers on the wafer, structures such as electrodes, leads and connections are formed to connect different parts of the device.