Standard CMOS / CMOS (4000) Logic Comparators
Reviewed by: Jon Lowy, consulting engineer
Description
Standard CMOS (4000 series) logic comparators are digital circuits that compare two binary numbers and determine their relative magnitudes. They output a binary signal indicating whether one number is greater than, less than, or equal to the other. These comparators are integral components in digital systems, providing essential comparison functions for various computational tasks.
Working Principle
CMOS logic comparators operate by using a combination of p-type and n-type metal-oxide-semiconductor field effect transistors (MOSFETs) to implement logic gates. These gates perform the comparison of input binary numbers by evaluating their relative magnitudes. The comparator outputs a binary signal based on the comparison, which is useful in digital systems for decision-making processes. The CMOS technology is favored for its low power consumption and high noise immunity, making these comparators efficient and reliable in various digital applications.
Applications
CMOS logic comparators are widely used in digital systems for tasks such as sorting algorithms, arithmetic operations, and digital signal processing. Specific examples include their use in microprocessors for decision-making processes, in digital communication systems for error detection and correction, and in embedded systems for real-time data analysis.
Advantages over other Logic Comparators
CMOS logic comparators offer several advantages over other types of logic comparators. They consume less power, especially when not switching, due to their rail-to-rail logic design. This makes them ideal for battery-powered and portable devices. Additionally, CMOS comparators have good power-supply rejection, which enhances their performance in environments with fluctuating power levels.
Limitations
One limitation of CMOS logic comparators is their slower speed compared to other logic families like emitter-coupled logic (ECL). This can be a drawback in applications requiring high-speed data processing. Additionally, CMOS comparators may have higher input offset voltages, which can affect their accuracy in certain applications.
Considerations
When selecting CMOS logic comparators, it is important to consider factors such as initial costs, which are generally lower due to the widespread use of CMOS technology. Operating expenses are minimized due to their low power consumption. However, their durability and accuracy can be influenced by environmental conditions, so proper design and shielding may be necessary. Replacement and maintenance costs are typically low, but it is crucial to ensure compatibility with existing systems to avoid additional expenses.
from Rochester Electronics
Magnitude Comparator, 4000/14000/40000 Series, 4-Bit, True Output, CMOS, CDIP16 [See More]
- Logic Family: CMOS
- Package Type: DIP; Other; CDIP16
- Type: Magnitude
from RS Components, Ltd.
Renesas Electronics 74FCT521ATSOG [See More]
- Logic Family: CMOS; CMOS
- Number of Bits: 8
- Number of Pins: 20
from Nexperia B.V.
The 74HC85; 74HCT85 is a 4-bit magnitude comparator that can be expanded to almost any length. They perform comparison of two 4-bit binary, BCD or other monotonic codes and present the three possible magnitude results at the outputs (QA >B, QA=B and QA <B). The 4-bit inputs are weighted (A0 to... [See More]
- Logic Family: CMOS
- Supply Voltage: 2.5V; 3V; 3.3V; 3.6V; 5V; Other; 2.0 - 6.0
- Type: Magnitude
- Features: ESD Protection
from Rochester Electronics
Identity Comparator, AC Series, 8-Bit, Inverted Output, CMOS, PDIP20 [See More]
- Logic Family: CMOS
- Package Type: DIP; Other; DIP20
- Type: Identity
from Nexperia B.V.
The 74HC85; 74HCT85 is a 4-bit magnitude comparator that can be expanded to almost any length. They perform comparison of two 4-bit binary, BCD or other monotonic codes and present the three possible magnitude results at the outputs (QA >B, QA=B and QA <B). The 4-bit inputs are weighted (A0 to... [See More]
- Logic Family: CMOS
- Supply Voltage: 2.5V; 3V; 3.3V; 3.6V; 5V; Other; 2.0 - 6.0
- Type: Magnitude
- Features: ESD Protection
from Rochester Electronics
74AC521 - Identity Comparator, AC Series, 8-Bit, Inverted Output, CMOS, PDIP20 [See More]
- Logic Family: CMOS
- Package Type: DIP; PDIP; Other; PDIP
- Type: Identity
from Nexperia B.V.
The 74HC688 is an 8-bit magnitude comparator. It performs comparisons of two 8 - bit binary or BCD words. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC. Features and benefits. Compare two 8-bit words. [See More]
- Logic Family: CMOS
- Supply Voltage: 2.5V; 3V; 3.3V; 3.6V; 5V; Other; 2.0 - 6.0
- Type: Magnitude
- Features: ESD Protection
from Rochester Electronics
74AC521 - Identity Comparator, AC Series, 8-Bit, Inverted Output, CMOS [See More]
- Logic Family: CMOS
- Package Type: SOIC; Other; SOIC20
- Type: Identity
from Nexperia B.V.
The 74HC688 is an 8-bit magnitude comparator. It performs comparisons of two 8 - bit binary or BCD words. Inputs include clamp diodes. This enables the use of current limiting resistors to interface inputs to voltages in excess of VCC. Features and benefits. Compare two 8-bit words. [See More]
- Logic Family: CMOS
- Supply Voltage: 2.5V; 3V; 3.3V; 3.6V; 5V; Other; 2.0 - 6.0
- Type: Magnitude
- Features: ESD Protection
from Rochester Electronics
Identity Comparator, AC Series, 8-Bit, Inverted Output, CMOS, PDSO20 [See More]
- Logic Family: CMOS
- Package Type: SOP; Other; SOP20
- Type: Identity
from Rochester Electronics
Identity Comparator, AC Series, 8-Bit, Inverted Output, CMOS, PDSO20 [See More]
- Logic Family: CMOS
- Package Type: SOP; SSOP; TSSOP; Other; TSSOP20
- Type: Identity
from Rochester Electronics
Magnitude Comparator, 4000/14000/40000 Series, 4-Bit, Inverted Output, CMOS, PDIP16 [See More]
- Logic Family: CMOS
- Package Type: DIP; Other; DIP16
- Type: Magnitude
from Rochester Electronics
Magnitude Comparator, 4000/14000/40000 Series, 4-Bit, Inverted Output, CMOS, PDSO16 [See More]
- Logic Family: CMOS
- Package Type: SOP; Other; SOP16
- Type: Magnitude
from Rochester Electronics
Magnitude Comparator, 4000/14000/40000 Series, 4-Bit, Inverted Output, CMOS, PDSO16 [See More]
- Logic Family: CMOS
- Package Type: SOIC; Other; SOIC-16
- Type: Magnitude
from Integrated Device Technology
The IDT74FCT521T is an 8-bit identity comparator that compares two words of up to eight bits each and provides a low output when the two words match bit for bit. The expansion input IA = B also serves as an active low enable input. The 74FCT521T operates at -40C to +85C [See More]
- Logic Family: TTL; CMOS
- Supply Voltage: 5V
- Type: Identity
- Package Type: Other; QSOP
from Utmel Electronic Limited
IC COMP 1.8V P-P R-R I/O SC70-5 [See More]
- Logic Family: CMOS; BICMOS
- Package Type: SSOP; Other; 5-TSSOP, SC-70-5, SOT-353
- Supply Voltage: 5V; Other; 2.7V
- Number of units in IC: 1
from Utmel Electronic Limited
IC COMP 1.8V SNGL R-R IN SOT23-5 [See More]
- Logic Family: CMOS; BICMOS
- Package Type: Other; SC-74A, SOT-753
- Supply Voltage: 5V; Other; 1.8V
- Number of units in IC: 1
from Utmel Electronic Limited
IC COMP DUAL 1.8V RRI 8-USMD [See More]
- Logic Family: CMOS; BICMOS
- Package Type: Other; 8-WFBGA
- Supply Voltage: Other; 1.8V
- Number of units in IC: 2
from Utmel Electronic Limited
IC COMP DUAL MICRPWR CMOS 8-SOIC [See More]
- Logic Family: CMOS; CMOS
- Package Type: SOIC; Other; 8-SOIC (0.154, 3.90mm Width)
- Supply Voltage: 5V; Other; 5V
- Number of units in IC: 2
from Utmel Electronic Limited
IC COMP DUAL P-P NANOPWR 8SOIC [See More]
- Logic Family: CMOS; CMOS
- Package Type: SOIC; Other; SOIC
- Supply Voltage: 5V; Other; 5V
- Number of Pins: 8
from Utmel Electronic Limited
IC COMP SNGL CMOS PP/OD SC88A [See More]
- Logic Family: CMOS; CMOS
- Package Type: SSOP; Other; 5-TSSOP, SC-70-5, SOT-353
- Supply Voltage: Other; 3V
- Number of units in IC: 1
from Utmel Electronic Limited
IC COMP TINY DUAL LOW V 8VSSOP [See More]
- Logic Family: CMOS; BICMOS
- Package Type: SSOP; Other; 8-TSSOP, 8-MSOP (0.118, 3.00mm Width)
- Supply Voltage: Other; 2.7V
- Number of units in IC: 2