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The Ultimate Guide to 74ls vs. 74hc series ICs

Updatezeit: 2023-09-21 17:33:38


The realm of Integrated Circuits (ICs) is rapidly expanding, giving rise to various evolving technologies. The most commonly used and discussed of ICs are 74LS and 74HC. This comprehensive guide lets us explore the differences between 74LS and 74HC series ICs. By delving into this comparative analysis, we understand how each series contributes uniquely to the ever-expanding technological landscape.

Overview of 74LS and 74HC Series ICs

74LS and 74HC series ICs belong to the TTL (Transistor-Transistor Logic) and CMOS (Complementary Metal-Oxide-Semiconductor) logic families. The nomenclature 'TTL series' remains closely associated with the 74 series, despite the contemporary ICs diverging from TTL technology. In contrast, the 74HC family showcases swifter CMOS circuitry, seamlessly fusing the velocity akin to TTL with the notably frugal power requisites synonymous with the 4000 series. These ICs adhere to CMOS architecture while retaining pin configurations reminiscent of their predecessor, the 74LS family.


What is the Difference between 74ls and 74hc?

The difference between the 74LS and 74HC series of electronic circuits encompass the following:

  1. LS embodies a low-power Schottky configuration, while HC operates as a high-speed COMS counterpart. LS marginally surpasses HC in terms of speed, with HCT presenting compatibility with LS inputs and outputs while exhibiting reduced power consumption. Meanwhile, F introduces a high-speed Schottky circuit.

  2. While LS adheres to the TTL level, HC functions at the CMOS level.

  3. LS permits an open high-level input, while HC prohibits open inputs. HC necessitates pull-up and pull-down resistors to determine invalid input levels. In contrast, LS does not demand such provisions.

  4. LS boasts robust pull-down capabilities and relatively weaker pull-up strengths. HC maintains parity in pull-up and pull-down effectiveness.

  5. Divergence in operating voltages is evident; LS confines itself to 5V, while HC accommodates a range from 2V to 6V.

  6. The differentiation extends to signal levels. LS embodies TTL levels with low and high thresholds of 0.8V and 2.4V, respectively. Conversely, CMOS signifies low and high levels at 0.3V and 3.6V within a 5V operational scope. This permits CMOS to drive TTL, but the converse remains implausible.

  7. The disparity extends to driving capabilities. LS showcases high-level driving capacity at around 5mA and low-level prowess at approximately 20mA. In contrast, CMOS maintains parity at 5mA for both high and low levels.

  8. CMOS components exhibit susceptibility to static discharge and are prone to latching predicaments. Consequently, CMOS input pins should not directly interface with power sources.

74ls74 Circuit

74ls74 Circuit.jpg

Other 74LS Series ICs

74LS181 ,74LS138 ,74LS74 ,74LS47 ,74LS32 ,74LS04 ,74LS00  ,SN74HC138N ,74HC138 ,74LS08

74hc00 Circuit

The 74HC00 is a 14-pin IC with four independent gates, each designed for the logic NAND operation. Utilizing advanced silicon-gate CMOS technology, this device achieves operational speeds akin to LS-TTL gates, all while demonstrating reduced power consumption compared to conventional CMOS ICs.

74hc00 Circuit.png

Performance Comparison

  • The 74LS series is called "Low Power Schottky TTL," collectively known as the 74LS series. An enhanced version is the "Advanced Low Power Schottky TTL," namely the 74ALS series, which offers better performance than the 74LS.

TTL Circuit.jpg

  • The 74HC series possesses the low-power attributes of CMOS and a performance level comparable to the high-speed characteristics of the 74LS. This series represents a high-speed, low-power product.


The 74HC is part of the CMOS series, characterized by its elevated input impedance, higher output voltage (where 4.9V indicates logic 1), and comparatively limited driving capability. On the other hand, the 74LS falls within the TTL series, featuring lower output voltage (3.5V representing logic 1) and a more robust driving capacity. While the correlation with microcontrollers isn't paramount, it is recommended to opt for chips of a consistent type, preferably the 74HC series.

Applications Comparison

The 74HC and 74LS sets of integrated circuits (ICs) have distinctive attributes impacting their utility across diverse electronic configurations. Presented here is an overview of their typical applications:

Applications of the 74HC Series

  • High-Speed Logic Circuits: The 74HC series distinguishes itself through its prowess in high-speed domains, rendering it apt for scenarios necessitating swift signal handling and data manipulation. It frequently finds application within high-frequency digital logic assemblies, encompassing clock dispersion, data routing, and expeditious data transmission.

  • Microcontroller and FPGA Interaction: Given its elevated velocity profile, the 74HC series commonly interfaces with microcontrollers, microprocessors, and field-programmable gate arrays (FPGAs). This assists in enabling streamlined communication between these components and other peripheral entities.

  • Chronological Generation and Harmonization: Elements from the 74HC series are employed in chronicle creation, synchronization, and frequency division contexts. Their role entails guaranteeing precision in timing and synchronization facets within systems characterized by stringent temporal requisites.

  • Bidirectional Information Transceivers and Gradient Adjusters: The 74HC series is harnessed for two-way data propagation across diverse sectors of a circuit or between dissimilar voltage realms. Additionally, it serves as a gradient adjuster, ensuring effective communication between constituents operating at differing voltage thresholds.

  • Serialized Interaction Interfaces: ICs deriving from the 74HC series demonstrate utility in serialized interaction protocols, encompassing avenues such as SPI (Serial Peripheral Interface) and I2C (Inter-Integrated Circuit). The high-speed attributes of these ICs render them conducive to swift data exchange within such applications.

  • Catalyzing Digital Display Conduction: The 74HC series effectively steers digital displays, LEDs, and analogous visual indicators, necessitating prompt response intervals and high-velocity transitions.


Applications of the 74LS Series

  • Standard Digital Logic Circuits: The 74LS series is widely embraced within general-purpose digital logic configurations, encompassing gate formations, flip-flops, multiplexing, and demultiplexing. Its harmonization with TTL voltage levels and robust performance renders it amenable to a spectrum of logical operations. The IC 74LS90 is often used in digital logic designs.

  • Interaction with Microcontrollers and Microprocessors: The 74LS series facilitates interaction between microcontrollers, microprocessors, and additional digital entities that interface with disparate peripherals or systems. This expedites data interchange and the conveyance of control signals amid these components.

  • Chronicle and Timing Assemblies: Elements from the 74LS series find application in chronicle creation, timing elucidation, and the execution of pulse width modulation (PWM) tactics. Their contribution extends to the precise generation of pulses and timing control.

  • Addressing and Elucidation of Memory Locations: The 74LS series finds utility in memory frameworks, where it aids in decoding addresses, thereby facilitating the pinpoint selection of designated memory locations.

  • Interfacing with Sensors: ICs from the 74LS series engage in interfaces with sensors and transducers to procure and process sensor-derived data.

  • Low-Speed Digital Signal Processing: Given its steadfast and enduring attributes, the 74LS series is well-suited for measured-speed digital signal processing endeavors that do not necessitate heightened-speed transitions.

  • Basic Control Logic: The 74LS series finds employment in rudimentary control logic operations spanning an array of contexts and applications.

The 74HC series is preferable for applications demanding rapidity, efficient signal processing, and elevated frequency operations. In contrast, the 74LS series commonly finds its niche within comprehensive logic arrangements, microcontroller interfaces, chronicle generation, and other undertakings necessitating dependable and tenacious performance characteristics at more modest speeds.


Within the ever-evolving realm of electronics, the decision between opting for either the 74LS or 74HC series of ICs encompasses a multitude of considerations. Through a comprehensive grasp of their disparities, operational attributes, and optimal utilities, you can astutely choose the most fitting ICs for your project. Whether engaged in pioneering technological innovation or indulging in hobbyist electronics, the insights acquired from this guide provide you with the tools to make enlightened choices, ultimately leading to remarkable accomplishments.

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  • Is 74HC compatible with 74LS?
  • Note that 74HC inputs may face challenges when driven by 74LS outputs due to contradictions in voltage ranges for logic 0. To circumvent this issue, it is advisable to employ 74HCT components instead. Notably, the 74HCT family presents a distinctive iteration of the 74HC series, featuring 74LS TTL-compatible inputs. This unique attribute renders the 74HCT series suitable for harmonizing with 74LS counterparts within a unified system.

  • What is the difference between LS and HC ICs?
  • The primary contrast between HC and LS lies in their logic thresholds. HC mandates a minimum input of 3.5 V@5Vcc to attain the high-level logic, whereas LS adheres to the customary TTL standard, designating anything surpassing 2.0 V@5Vcc as logic 1. Hence, cautious consideration is imperative when interfacing with the input of HC logic configurations.

  • What is the replacement for 74ls?
  • The 74HCT family represents a distinct iteration of 74HC, incorporating 74LS TTL-compatible inputs. This inherent compatibility empowers the seamless integration of 74HCT alongside 74LS within an identical framework. Notably, 74HCT holds the potential to serve as efficient, low-power alternatives to the preceding 74LS ICs in the majority of circuit configurations. More details about 74HCT can check on CD74HCT163E datasheet.

  • What is the difference between 74LS00 and 74HC00?
  • 74HC00 and 74LS00 share identical models. While 74HC00 operates as a high-velocity circuit, 74LS00 embodies a low-velocity counterpart. It is feasible for 74HC00 to replace 74LS00, yet the reverse is not attainable.

  • What are the similarities and differences between CD4011, 74LS00, and 74HC00?
  • CD4011, 74LS00, and 74HC00 all share the common trait of being 2-input four-NAND gates. However, distinctions arise in their pin configurations. While the pin arrangement differs between CD4011 and 74LS00/74HC00, the latter two exhibit matching pin layouts. CD4011 is a CMOS entity, functioning within a voltage range of 3V-18V. In contrast, 74LS00 operates as a TTL component, reliant upon a 5V power supply. 74HC00, identified as a high-velocity CMOS device, operates with a power supply voltage spanning 2V-6V.

  • What does LS and HC mean in IC number?
  • HC stands for high-speed CMOS, while LS stands for low-power Schottky, a technology rooted in bipolar principles. When comparing CMOS with bipolar (TTL), notable threshold-level variations emerged, rendering them inappropriate.

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