CD74HCT20E Datasheet: Analysis

The CD74HCT250E is an essential asset for creating designs that best leverage this NAND gate IC’s advantages.

The CD74HCT20E Datasheet provides essential design information for this popular IC.

When designing digital circuits, it is important to understand the symbols and functionality of common gate symbols, like the NAND or “NOT AND” gate. NAND gates are implemented in various types of digital devices and circuits, including arithmetic logic units (ALUs), decoders, encoders, and multiplexers. The popularity of these logic gates is derived from the fact that they can be used to create virtually any logic function or operation. In fact, it is not unusual to find entire circuits composed of only NAND gates. Most often, NAND gates come in IC packages consisting of multiple components. A good example of this is the CD74HCT20E datasheet, which includes essential design information for effectively implementing a DUAL NAND gate architecture.

CD74HCT20E: Features and Applications

From the CD74HCT20E datasheet, the versatile dual NAND gate component has the following features:

Features of the CD74HCT20E

LSTTL input logic compatible (VIL(max) = 0.8 V, VIH(min) = 2 V)
CMOS input logic compatible (II ≤ 1 µA at VOL, VOH
Buffered inputs
Operating range: 4.5 V to 5.5 V
Temperature operating range: -55°C to +125°C
Fanout range: 10 LSTTL loads
Significant power reduction compared to LSTTL logic ICs

This device offers a good generic solution for many important performance metrics; such as a fast switching speed of 15 ns, which enables high-speed operation and low power consumption, a standard operational objective for electronic systems that satisfies low current requirements. It also has a reasonable input voltage range that accommodates many power supply designs (typically around 5V) and high noise immunity that is advantageous in compact environments. These characteristics enable the CD74HCT20E to be used in various applications; including timing and control, industrial systems, and other functional applications, as shown below.

Typical Applications of the CD74HCT20E
Application Area	Utilization
Timing and Control Systems	Oscillator Buffer Debouncer Pulse Stretcher
Industrial Systems	Safety System Sensor Interface Motor Control
Functional Application	Power Management Microprocessors Peripherals and Memory Data Communications

CD74HCT20E: Important Electrical Characteristics

Parameter	Minimum	Typical	Maximum	Unit	Conditions
Supply Voltage (VCC)	4.5	5.0	5.5	V	Operating range
Input High Voltage (VIH)	2.0	-	-	V	Logic 1 recognition
Input Low Voltage (VIL)	-	-	0.8	V	Logic 0 recognition
Output High Voltage (VOH)	4.4	-	-	V	IOH = -4.0 mA
Output Low Voltage (VOL)	-	-	0.33	V	IOL = 4.0 mA
Propagation Delay (tPLH)	-	15	25	ns	CL = 50 pF
Propagation Delay (tPHL)	-	15	25	ns	CL = 50 pF
Power Consumption (ICC)	-	20	80	µA	Static conditions

In addition to the electrical characteristics above, the CD74HCT20E datasheet also informs the device operates reliably across industrial temperature ranges (-40°C to +85°C) and provides TTL-compatible input thresholds while maintaining CMOS power efficiency. This makes it ideal for mixed-signal designs where legacy TTL interfaces must communicate with modern CMOS circuitry.

CD74HCT20E: Pinout and Pin Descriptions

The CD74HCT20E pinout is shown below.

The pinout of the CD74HCT20E

As shown, the chip contains two 4-input NAND gates conveniently located on opposite sides of the IC package. The two independent 4-input NAND gates share common power and ground connections. All of the pin functions are listed below.

CD74HCT20E PIN DESCRIPTIONS
Pin	Symbol	Function	Description
1	1A	Input	Gate 1, Input A
2	1B	Input	Gate 1, Input B
3	1C	Input	Gate 1, Input C
4	1D	Input	Gate 1, Input D
5	1Y	Output	Gate 1, Output
6	2A	Input	Gate 2, Input A
7	GND	Power	Ground (0 V)
8	2Y	Output	Gate 2, Output
9	2B	Input	Gate 2, Input B
10	2C	Input	Gate 2, Input C
11	2D	Input	Gate 2, Input D
12	NC	-	No Connection
13	NC	-	No Connection
14	VCC	Power	Supply Voltage (+5 V)

Critical Connection Notes:

Unused inputs must be tied to VCC or GND to prevent floating states
Power supply decoupling requires a 0.1 µF ceramic capacitor between VCC and GND
Output loading should not exceed 4.0 mA sink or source current per gate
Input protection includes internal diode clamps to VCC and GND

CD74HCT20E: Operation and Circuit Example

The CD74HCT20E performs standard Boolean algebra AND operations between the four inputs. This results in the logic diagram for each gate below. NOTE: X indicates “Don’t Care” connections that have no effect on device operation.

Functional Diagram for CD74HCT20E NAND gates

The CD74HCT20E serves multiple functions in digital systems, from basic logic operations to complex timing circuits. Below, a common application of the device used to perform SR latch functionality is shown.

Example CD74HCT20E implementation

Alternative Components to the CD74HCT20E

There may be situations where using the CD74HCT20E is not a viable option. For example, if the device is not reliably available due to supply chain issues or is cost-prohibitive due to market fluctuations. A PCB design best practice for a robust component library is to compile a list of practical alternatives, as listed below, for the CD74HCT20E.

Part Number	Manufacturer	Technology	Key Differences
SN74HC20	Texas Instruments	CMOS	Lower power, 2 V minimum VCC
CD4012B	Texas Instruments	CMOS	Dual 4-input NAND, wide voltage range
74LS20	Various	TTL	Higher power, faster switching
MC74HCT20A	ON Semiconductor	HCT	Pin-compatible, similar specs

Using an alternative component is always a compromise and weighing the trade-offs should drive your final selection. Below are some tips for alternative selection, if necessary, to replace the CD74HCT20E.

CD74HCT20E Replacement Tips:

For power-sensitive designs

Choose 74HC20 for battery-powered applications

For legacy TTL compatibility

Stick with HCT variants for 5 V systems

For a wide voltage range

Consider CD4012B for 3 V to 18 V operation

For high-speed applications

Evaluate 74LS20 for sub-10 ns propagation delays

PCB Design with the CD74HCT20E Datasheet

Effective PCB design with the CD74HCT20E dual 4-input NAND gate begins with having accurate and comprehensive data and information. The CD74HCT20E datasheet is an essential source that provides much of the necessary design resources. However, it is also critical that you acquire and use an accurate schematic symbol, PCB footprint, and 3D CAD model (especially, for ECAD-MCAD designs), as shown below.

Schematic symbol, PCB footprint, and 3D CAD model of the CD74HCT20E from UL

Failing to do so will lead to inaccuracies in your schematic and layout, which can derail the building of your boards. To avoid these potential contingencies, you should always source CAD models and datasheets from trusted sources.

If you’re looking for CAD models for common components or important information for creating the best design from the CD74HCT20E datasheet, Ultra Librarian helps by compiling all your sourcing and CAD information in one place.

Working with Ultra Librarian sets up your team for success to ensure streamlined and error-free design, production, and sourcing. Register today for free.