It is well known that people have defined three basic logical relationships: AND, OR, NOT, which can be combined to form NAND, NOR, XOR, XNOR five logical relationships. All logical relationships in digital systems can be realized using the basic three logical relationships (similar to how decimal numbers can always be represented using 10 digits and a decimal point). The circuits that implement logical relationships are called logic gate circuits. Various gate circuits can be constructed using discrete components such as diodes,BJT, MOS transistors, resistors, capacitors, etc., but circuits made from discrete components are not very convenient to use. With the development of integrated technology, people are more accustomed to using integrated logic gate circuits. If the core components of the integrated logic gate circuit areBJT, it is called a TTL circuit (also known as bipolar circuit), and if the core components areMOS transistors, it is called aMOS circuit (also known as unipolar circuit). In Multisim, the models of integrated logic gates are usually based on international standard logic series (such as 74 series, CD4000 series) and also include manufacturer-specific models (such as TI, ON Semiconductor, etc.). These models cover basic logic functions such as AND gates, OR gates, NOT gates, NAND gates, NOR gates, XOR gates, XNOR gates, etc., as well as derived devices like buffers and drivers. Below, we introduce the common classifications and examples of integrated logic gate models in Multisim.
1.TTL Series (74xx Series) Logic Gates
TTL (Transistor-Transistor Logic) is an early mainstream logic series, Multisim includes several sub-series (such as 74LS, 74HC, 74HCT, etc.), among which 74LS (Low-Power Schottky) and 74HC (High-Speed CMOS, TTL compatible) are the most commonly used.
(1) Basic Logic Gates
AND Gate: 74LS08 (Quad 2-Input AND Gate), 74LS11 (Triple 3-Input AND Gate), 74LS21 (Dual 4-Input AND Gate); OR Gate: 74LS32 (Quad 2-Input OR Gate), 74LS4075 (Triple 3-Input OR Gate, some versions are 74LS51); NOT Gate (Inverter): 74LS04 (Hex Inverter), 74LS14 (Hex Schmitt Trigger Inverter, noise resistant); NAND Gate: 74LS00 (Quad 2-Input NAND Gate), 74LS10 (Triple 3-Input NAND Gate), 74LS20 (Dual 4-Input NAND Gate); NOR Gate: 74LS02 (Quad 2-Input NOR Gate), 74LS27 (Triple 3-Input NOR Gate); XOR Gate: 74LS86 (Quad 2-Input XOR Gate); XNOR Gate: 74LS266 (Quad 2-Input XNOR Gate, open-drain output) or needs to be implemented using XOR Gate + NOT Gate combination.
(2) Special Function Gates
Buffer/ Driver: 74LS07 (Hex High-Voltage Open-Drain Buffer, Output 30V), 74LS244 (Octal Buffer/Line Driver, Tri-State Output); Schmitt Trigger: 74LS132 (Quad 2-Input Schmitt NAND Gate), 74LS14 (Hex Schmitt Inverter).
2.CMOS Series (CD4000 Series) Logic Gates
CMOS (Complementary Metal-Oxide-Semiconductor) features low power consumption and high noise immunity, Multisim commonly includes CD4000 series (such as CD4011, CD4081, etc.), compatible with 5V power supply, and some models support wide voltage (3-18V).
(1) Basic Logic Gates
NAND Gate: CD4011 (Quad 2-Input NAND Gate), CD4023 (Triple 3-Input NAND Gate), CD4012 (Dual 4-Input NAND Gate); NOR Gate: CD4001 (Quad 2-Input NOR Gate), CD4025 (Triple 3-Input NOR Gate); AND Gate: CD4081 (Quad 2-Input AND Gate), CD4073 (Triple 3-Input AND Gate); OR Gate: CD4071 (Quad 2-Input OR Gate), CD4075 (Triple 3-Input OR Gate); NOT Gate: CD4069 (Hex Inverter, Non-Bufferring), CD4049 (Hex Inverter Buffer, Enhanced Drive); XOR Gate: CD4030 (Quad 2-Input XOR Gate).
(2) Special Function Gates
Buffer: CD4050 (Hex Buffer, High Voltage Output), CD4069UB (Hex Inverter, No Buffer Stage, Suitable for High Frequency).
3. Other Common Series Logic Gate Circuits
74HC/HCT Series (High-Speed CMOS, TTL Compatible): such as 74HC00 (Quad 2-Input NAND Gate, replacing 74LS00), 74HCT86 (Quad 2-Input XOR Gate, TTL level compatible). Manufacturer-specific models: Multisim includes TI (such as SN74LS00), ON Semiconductor (such as MC74HC00) and other manufacturers’ specific models, but their functions are consistent with international standard models.
4. Methods to Find Logic Gate Circuits
In Multisim, you can quickly find logic gate circuits through the following paths:
(1) Open the component library (Place ā Component);
(2) Select Group: Group ā TTL (to find 74xx series) or Group ā CMOS (to find CD4000 series);
(3) Filter Family (Family): such as 74LS, 74HC, CD4000 etc.;
(4) Search keywords (such as “AND”, “NAND”, “XOR”) or specific models (such as “74LS00”).
5. Precautions
(1) Different sub-series (such as 74LS vs 74HC) have different power supply voltages (74LS is usually 5VĀ±5%, 74HC can be 2-6V) and driving capabilities, and should be selected according to circuit requirements.
(2) Some models may have “open-drain output” (such as 74LS07, CD4011 some pins), and an external pull-up resistor is required to output a high level normally.
(3) The component library of Multisim may vary slightly due to different versions, it is recommended to directly search for the model using the “Search” function to confirm.
The above models can cover the needs of most basic logic gate circuits in digital circuits. In practical use, it is advisable to prioritize commonly used models (such as 74LS00, CD4011) to ensure simulation compatibility.