LF444CMX Equivalent & Substitute Parts

Part Overview

The LF444CMX is a J-FET input operational amplifier with four independent circuits in a 14-SOIC surface mount package, manufactured by Texas Instruments. This device is classified as obsolete, which necessitates identification of equivalent and substitute components for new designs and ongoing production support. The LF444CMX operates across a ±18V supply range with a 1 MHz gain bandwidth product and 1V/µs slew rate, making it suitable for precision signal conditioning applications requiring low input bias current.

Key Parameters

Parameter	Value	Unit
Amplifier Type	J-FET	—
Number of Circuits	4	—
Slew Rate	1	V/µs
Gain Bandwidth Product	1	MHz
Current - Input Bias	10	pA
Voltage - Input Offset	3	mV
Current - Supply (x4 Channels)	600	µA
Current - Output / Channel	14	mA
Voltage - Supply Span	36	V
Operating Temperature	0 to 70	°C
Package / Case	14-SOIC (0.154", 3.90mm Width)	—
Mounting Type	Surface Mount	—
RoHS Status	RoHS non-compliant	—

Substitute Part Grouping Explanation

Substitution of the LF444CMX is determined by strict alignment of electrical and mechanical parameters. The primary substitution criteria are:

Critical Parameters for Substitution:

Amplifier Type (J-FET vs. General Purpose)
Number of Circuits (4 independent channels required)
Package / Case (14-SOIC form factor)
Mounting Type (Surface Mount)
Supply Voltage Range compatibility
Input Bias Current characteristics
Slew Rate and Gain Bandwidth Product

Substitution Categories:

Category 1: Direct Equivalent (Same Amplifier Type) LF444CMX/NOPB is the direct equivalent with identical electrical specifications but active product status and RoHS3 compliance. LF247DT, LF347D, and LF347DT are J-FET amplifiers with enhanced performance characteristics (higher slew rate, increased gain bandwidth product, higher output current) while maintaining the same package and four-circuit configuration.

Category 2: Functional Alternatives (Different Amplifier Type) LM2902AQS14-13, LM2902DT, LM2902EDR2G, LM2902VDR2G, and LM324DR2G are general-purpose operational amplifiers with four circuits in 14-SOIC packaging. These devices differ in amplifier topology (general purpose vs. J-FET) and have different electrical characteristics, including lower input bias current (nanoampere range vs. picoampere range) and different supply voltage ranges.

Category 3: Premium J-FET Alternative LT1465CS#PBF is a J-FET amplifier with superior input bias current (0.5 pA) and lower input offset voltage (600 µV), though with different supply voltage range and operating temperature specifications.

Parameter Comparison

Parameter	LF444CMX	LF444CMX/NOPB	LF247DT	LF347D	LF347DT	LM2902AQS14-13	LM2902DT	LM2902EDR2G	LM2902VDR2G	LM324DR2G	LT1465CS#PBF
Amplifier Type	J-FET	J-FET	J-FET	J-FET	J-FET	General Purpose	General Purpose	General Purpose	General Purpose	General Purpose	J-FET
Number of Circuits	4	4	4	4	4	4	4	4	4	4	4
Slew Rate (V/µs)	1	1	16	16	16	0.3	0.3	—	—	—	0.9
Gain Bandwidth Product (MHz)	1	1	4	3	4	0.7	0.8	—	1	1	1
Current - Input Bias (pA/nA)	10 pA	10 pA	20 pA	20 pA	20 pA	20 nA	20 nA	90 nA	90 nA	90 nA	0.5 pA
Voltage - Input Offset (mV/µV)	3 mV	3 mV	3 mV	3 mV	3 mV	2 mV	1 mV	2 mV	2 mV	2 mV	600 µV
Current - Supply (µA)	600	600	1400	1400	1400	1000	1000	—	—	—	145
Current - Output / Channel (mA)	14	14	40	40	40	40	30	40	40	40	—
Voltage - Supply Span (V)	36	36	44	44	44	2–36	3–32	3–32	3–32	3–32	10–30
Operating Temperature (°C)	0 to 70	0 to 70	−40 to 105	0 to 70	0 to 70	−40 to 125	−40 to 125	−40 to 105	−40 to 125	0 to 70	−40 to 85
Package / Case	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC	14-SOIC
Product Status	Obsolete	Active	Active	Active	Active	Active	Not For New Designs	Active	Active	Active	Active
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Performance):

LF444CMX/NOPB is the recommended direct substitute. This part maintains identical electrical specifications (1V/µs slew rate, 1 MHz gain bandwidth product, 10 pA input bias current, 3 mV input offset voltage) and identical package configuration. The primary advantage is active product status and RoHS3 compliance, eliminating obsolescence risk and supporting modern supply chain requirements.

For Enhanced Performance Applications:

LF247DT and LF347DT offer improved performance characteristics within the J-FET amplifier category. Both devices provide 16V/µs slew rate (16× improvement) and 4 MHz gain bandwidth product (4× improvement), with increased output current capability (40 mA vs. 14 mA). These substitutes are suitable when circuit design permits higher performance specifications. LF347D provides identical performance to LF347DT with different packaging (Tube vs. Cut Tape & Digi-Reel).

For Cost-Optimized Applications:

LM324DR2G and LM2902VDR2G are general-purpose operational amplifiers with active product status and RoHS3 compliance. These devices operate across a 3–32V supply range and provide 1 MHz gain bandwidth product. The trade-off is higher input bias current (90 nanoamperes vs. 10 picoamperes), which may impact precision applications requiring extremely low input current. These alternatives are suitable for applications where input bias current specifications are non-critical.

For Extended Temperature Range:

LM2902AQS14-13 and LM2902VDR2G support operating temperatures from −40°C to 125°C, exceeding the LF444CMX specification of 0°C to 70°C. LM2902AQS14-13 includes AEC-Q100 automotive qualification. These devices are appropriate for industrial and automotive applications requiring extended temperature operation.

For Premium Precision Applications:

LT1465CS#PBF is a J-FET amplifier with superior input bias current (0.5 pA) and input offset voltage (600 µV), representing the lowest noise and highest precision option. This device is suitable for instrumentation and precision measurement applications where input characteristics are critical. Supply voltage range (10–30V) and operating temperature range (−40°C to 85°C) differ from the original specification.

Devices Not Recommended for New Designs:

LM2902DT carries a "Not For New Designs" product status designation and should be avoided for new development projects despite active inventory availability.

Frequently Asked Questions (FAQ)

Q1: Can LF444CMX/NOPB be used as a direct drop-in replacement for LF444CMX?

A: Yes. LF444CMX/NOPB is electrically and mechanically identical to LF444CMX, with the same 14-SOIC package, four-circuit configuration, and all electrical specifications (1V/µs slew rate, 1 MHz gain bandwidth product, 10 pA input bias current). The primary differences are active product status and RoHS3 compliance. No circuit modifications are required.

Q2: What is the key difference between J-FET and general-purpose amplifier substitutes?

A: J-FET amplifiers (LF444CMX, LF247DT, LF347DT, LT1465CS#PBF) feature extremely low input bias current in the picoampere range, making them suitable for high-impedance signal sources and precision applications. General-purpose amplifiers (LM2902, LM324) have input bias current in the nanoampere range, approximately 1000× higher. Selection depends on whether the application circuit can tolerate this input current level.

Q3: Can LF247DT or LF347DT be used in place of LF444CMX without circuit redesign?

A: Electrical substitution is possible because both devices maintain the same package (14-SOIC), four-circuit configuration, and J-FET input characteristics. However, the enhanced performance specifications (16V/µs slew rate vs. 1V/µs, 4 MHz gain bandwidth product vs. 1 MHz) may affect circuit behavior in applications with tight bandwidth or slew rate constraints. Circuit verification is necessary to confirm compatibility with existing designs.

Q4: Are general-purpose amplifiers (LM324, LM2902) suitable replacements for precision measurement circuits?

A: General-purpose amplifiers can replace LF444CMX only in applications where input bias current specifications are non-critical. The 90 nanoampere input bias current of LM324DR2G and LM2902VDR2G is approximately 9000× higher than the 10 picoampere specification of LF444CMX. In high-impedance circuits or precision instrumentation, this difference will introduce significant measurement error. Verify input impedance and bias current requirements before substitution.

Q5: What is the significance of RoHS3 compliance for substitute selection?

A: RoHS3 compliance indicates the device meets Restriction of Hazardous Substances regulations, eliminating lead and other restricted materials. The original LF444CMX is RoHS non-compliant. All recommended substitutes (LF444CMX/NOPB, LF247DT, LF347DT, LM2902 variants, LM324DR2G, LT1465CS#PBF) are RoHS3 compliant, supporting modern manufacturing and environmental requirements. For new designs and production, RoHS3 compliance is mandatory in most markets.

Q6: Does package compatibility guarantee functional interchangeability?

A: No. While all substitute parts use the 14-SOIC package with identical physical dimensions (0.154" width, 3.90mm), functional interchangeability depends on electrical parameter alignment. Package compatibility ensures mechanical fit on printed circuit boards, but electrical specifications (supply voltage range, input bias current, slew rate, gain bandwidth product) must match application requirements. Always verify electrical specifications before substitution.

Q7: Which substitute offers the best performance-to-cost ratio?

A: LM324DR2G provides the lowest-cost option with active product status, RoHS3 compliance, and 1 MHz gain bandwidth product matching the original specification. However, the 90 nanoampere input bias current represents a significant trade-off for precision applications. For applications where input bias current is acceptable, LM324DR2G offers cost optimization. For precision applications requiring low input bias current, LF444CMX/NOPB is the recommended choice despite higher cost.

Q8: Can LT1465CS#PBF be used in all applications where LF444CMX is specified?

A: LT1465CS#PBF offers superior precision characteristics (0.5 pA input bias current, 600 µV input offset voltage) but operates within a 10–30V supply range, compared to the LF444CMX specification of ±18V (36V span). Verify that the application circuit operates within this narrower supply voltage window. Operating temperature range (−40°C to 85°C) also differs from the original (0°C to 70°C). Substitution is appropriate only when supply voltage and temperature specifications are compatible.

Q9: What inventory considerations apply to substitute selection?

A: LF444CMX/NOPB (30,100 units), LM324DR2G (105,300 units), and LM2902VDR2G (45,400 units) have substantial inventory availability. LF247DT (17,352 units) and LF347DT (27,321 units) provide adequate stock for J-FET alternatives. LT1465CS#PBF (5,145 units) has limited availability. For long-term production support, devices with higher inventory levels reduce supply chain risk.

Q10: Is LM2902DT suitable for new designs despite active inventory?

A: No. LM2902DT carries a "Not For New Designs" product status designation. Although 105,100 units are in stock, this classification indicates the manufacturer is discontinuing the product line. For new development projects, select from devices with "Active" product status: LF444CMX/NOPB, LF247DT, LF347D, LF347DT, LM2902AQS14-13, LM2902EDR2G, LM2902VDR2G, LM324DR2G, or LT1465CS#PBF.

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