The most widely used digital circuits at present are TTL circuits and CMOS circuits. The TTL circuit uses a bipolar transistor as a switching element, so it is also called a bipolar integrated circuit. A bipolar digital integrated circuit is a device that conducts electrical conduction using carriers having two different polarities of electrons and holes. It has the advantages of high speed (fast switching speed) and strong driving ability, but its power consumption is relatively high and its integration is relatively low. According to the different applications, it is divided into 54 series and 74 series. The former is military products, and the latter is generally used in general industrial equipment and consumer electronics products. The 74 series digital integrated circuits are international standard circuits. Its varieties are divided into six categories: 74 & TImes; & TImes; (Standard), 74S & TImes; & TImes; (Schottky), 74LS × × (Low Power Schottky), 74AS × × (Advanced Schottky), 74ALS × × (Advanced low-power Schottky), 74F × × (high-speed), its logic function is exactly the same. MOS circuits, also known as field effect integrated circuits, belong to unipolar digital integrated circuits. In a monopolar digital integrated circuit, only one polarity of carriers (electrons or holes) is used for electrical conduction. Its main advantages are high input impedance, low power consumption, strong anti-interference ability and suitability for large-scale integration. In particular, its leading product CMOS integrated circuit has special advantages. For example, the static power consumption is almost zero, the output logic level can be VDD or VSS, and the rise and fall times are in the same order of magnitude. Therefore, CMOS integrated circuit products have become integrated circuits. One of the mainstream. Its variety includes 4000 series CMOS circuits and 74 series high speed CMOS circuits. The 74 series of high-speed CMOS circuits are divided into three major categories: HC is the CMOS operating level; HCT is the TTL operating level (which can be used interchangeably with the 74LS series); HCU is suitable for CMOS circuits without buffer stages. The logic functions and pinouts of the 74 series high-speed CMOS circuits are the same as those of the corresponding 74LS series. The operating speed is also very high and the power consumption is greatly reduced. The 74 series can be said to be the most common chip that we usually touch. The 74 series is divided into many types. The most commonly used ones are the following: 74LS, 74HC, and 74HCT. Input level Output level 74LS TTL Level TTL Level 74HC COMS Level COMS Level 74HCT TTL level COMS level In addition, with the introduction of BiCMOS integrated circuits, it combines the advantages of bipolar and MOS integrated circuits. The advantages of ordinary bipolar gate circuits are gradually disappearing, and some of the once dominant TTL series products are gradually withdrawing from the market. CMOS gate circuits continue to improve processes, and are moving in the direction of high speed, low power consumption, large drive capability, and low power supply voltage. BiCMOS integrated circuit input gate circuit using CMOS technology, the output of bipolar push-pull output, both with the advantages of CMOS, but also has the advantages of bipolar, has become the new favorite of integrated circuits. Low power consumption CMOS integrated circuits use field effect transistors and are complementary structures. Two FETs in series are always in the state where one tube is turned on and the other tube is turned off. The static power consumption of the circuit is theoretically zero. In fact, CMOS circuits still have a small amount of static power due to leakage currents. The typical power consumption of a single gate is only 20mW, and the dynamic power consumption (at 1MHz operating frequency) is only a few mW. Wide operating voltage range CMOS integrated circuits provide a simple power supply, and the power supply is small in size, and there is basically no need for voltage regulation. Domestic CC4000 series integrated circuits can work normally under 3~18V voltage. Large swing in logic The logic high level "1" and the logic low level "0" of the CMOS integrated circuit are close to the power supply high potential VDD and the power supply low potential VSS, respectively. When VDD=15V and VSS=0V, the output logic swing is approximately 15V. Therefore, the voltage utilization factor of CMOS integrated circuits is higher in various types of integrated circuits. Strong anti-interference ability The voltage noise margin of a CMOS integrated circuit is typically 45% of the supply voltage, guaranteed to be 30% of the supply voltage. As the supply voltage increases, the absolute value of the noise margin voltage will increase proportionally. For a supply voltage of VDD=15V (when VSS=0V), the circuit will have about 7V noise margin. High input impedance The inputs of CMOS integrated circuits are generally protected by protection diodes and series resistors, so they are slightly smaller than the input resistance of common FETs. However, these protection diodes are reverse biased within the normal operating voltage range. The DC input impedance depends on the leakage current of these diodes. Usually, the equivalent input impedance is as high as 103 to 1011 Ω. Therefore, the CMOS integrated circuit consumes almost no power from the drive circuit. Good temperature stability Because the power consumption of the CMOS integrated circuit is very low, the internal heat generation is small, and the circuit structure and electrical parameters of the CMOS circuit have symmetry. When the temperature environment changes, some parameters can play an automatic compensation function, so the CMOS integrated circuit The temperature characteristics are very good. The circuit of the general ceramic metal package, the operating temperature is -55 ~ +125 °C; plastic package circuit operating temperature range of -45 ~ +85 °C. Strong fanout capability Fanout capability is expressed by the number of inputs that the circuit output can drive. Since the input impedance of a CMOS integrated circuit is extremely high, the output capability of the circuit is limited by the input capacitance. However, when a CMOS integrated circuit is used to drive the same type, it is generally possible to drive more than 50 inputs without considering the speed. Strong anti-radiation ability The basic device in a CMOS integrated circuit is a MOS transistor belonging to a majority carrier conduction device. Various radiations and radiations have limited effects on their electrical conductivity, and are therefore particularly suitable for the production of aerospace and nuclear test equipment. Good controllability The rising and falling time of the output waveform of the CMOS integrated circuit can be controlled. Typical values ​​of the rise and fall times of the output of the CMOS integrated circuit are 125% to 140% of the transmission delay time of the circuit. Convenient interface Because the CMOS integrated circuit has high input impedance and large output swing, it is easy to be driven by other circuits and it is easy to drive other types of circuits or devices. ++++++++++++++++++++++++++++++++++++++ TTL-Transistor-Transistor Logic Triode-Transistor Logic MOS—Metal-Oxide Semiconductor Metal Oxide Semiconductor Transistors CMOS - Complementary Metal-Oxide Semiconductor Complementary Metal Oxide Semiconductor Transistor +++++++++++++++++++++++++++++++++++++++ Q: Why is BJT faster than CMOS? A: Many people only know that BJT is faster than CMOS, but they do not know why. Mainly affected by the mobility. Taking an NPN tube and an NMOS as examples, the mobility in the BJT is the bulk mobility, which is approximately 1350 cm2/vs. In NMOS, the semiconductor surface mobility is about 400-600cm2/vs. So the BJT's transconductance is higher than that of MOS, which is faster than MOS. This is why NPN (NMOS) is faster than PNP (PMOS). The reason why NPN is faster than PNP is also because the carrier mobility is different. The minority in the NPN base is electrons and the mobility is high (about 1350). The minority of the base of PNP is a hole (about 480). So the same structure and size of the pipe, NPN faster than PNP. Therefore, in the bipolar process, the NPN tube is the main method, and the PNP is made on the basis of compatibility. The MOS process is mainly based on the N-well PSUB process. This process can be used as a parasitic PNP tube. To do NPN tube is a P-well NSUB process. The reason why BJT is called bipolar is that there are both holes and electrons in the base region, and both carriers participate in conduction; however, only one type of carrier in the inversion layer of a MOS device participates in conduction. However, it is not because the total mobility of the two carriers is large. And the situation may be exactly the opposite. Because carrier mobility is related to temperature and doping concentration. The higher the semiconductor doping concentration, the smaller the mobility. In BJT, the low birth rate plays a major role. The reason why the NPN pipe is faster than the PNP pipe is that the NPN base is the electron of the base, the PNP is the hole, and the electron mobility is larger than the hole. NMOS is also faster than PMOS. The reason why NPN is faster than NMOS is that NPN is a bulk device, its carrier mobility is the mobility within a semiconductor, NMOS is a surface device, and its carrier mobility is the surface mobility (because the inversion layer is The surface under the gate oxide forms). The bulk mobility of semiconductors is greater than the surface mobility. Introducing the LiFePO4 Battery, the energy-efficient and long-lasting power source perfect for both emergency lights and exit signs. 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