LF351MX JFET Operational Amplifier Equivalent & Substitute Parts

Part Overview

The LF351MX is a J-FET input operational amplifier manufactured by onsemi, housed in an 8-SOP surface mount package. This device is classified as obsolete, which necessitates identification of active equivalent and substitute components for new designs or production continuity. The LF351MX serves applications requiring low input bias current and moderate bandwidth performance in a compact surface mount form factor.

Key Parameters

Parameter	Value	Unit
Amplifier Type	J-FET	—
Number of Circuits	1	—
Slew Rate	13	V/µs
Gain Bandwidth Product	4	MHz
Current - Input Bias	50	pA
Voltage - Input Offset	5	mV
Current - Supply	2.3	mA
Operating Temperature	0 to 70	°C
Mounting Type	Surface Mount	—
Package / Case	8-SOIC (0.154", 3.90mm Width)	—
Moisture Sensitivity Level	1 (Unlimited)	—

Substitute Part Grouping Explanation

Substitution of the LF351MX is determined by strict alignment of electrical and mechanical parameters. The following criteria establish valid substitution relationships:

Primary Substitution Criteria:

Amplifier Type: J-FET (required)
Number of Circuits: 1 (required)
Package / Case: 8-SOIC or 8-SOP (required for mechanical compatibility)
Operating Temperature Range: Must encompass or match 0°C to 70°C minimum
Mounting Type: Surface Mount (required)

Secondary Compatibility Parameters:

Slew Rate: 13 V/µs baseline; higher values acceptable
Gain Bandwidth Product: 4 MHz baseline; higher values acceptable
Current - Input Bias: 50 pA baseline; lower values acceptable
Voltage - Input Offset: 5 mV baseline; lower values acceptable
Current - Supply: 2.3 mA baseline; lower values acceptable

Substitute parts are grouped into two categories: Direct Equivalents (same base product number, different manufacturer or packaging) and Functional Alternatives (different base product number, compatible electrical specifications).

Parameter Comparison

Part Number	Manufacturer	Product Status	Slew Rate (V/µs)	GBW (MHz)	Input Bias (pA)	Input Offset (mV)	Supply Current (mA)	Temp Range (°C)	Package
LF351MX	onsemi	Obsolete	13	4	50	5	2.3	0 to 70	8-SOP
LF351D	STMicroelectronics	Active	16	4	20	3	1.4	0 to 70	8-SOIC
LF351DT	STMicroelectronics	Active	16	4	20	3	1.4	0 to 70	8-SOIC
LF356M/NOPB	Texas Instruments	Active	12	5	30	3	5	0 to 70	8-SOIC
LF356MX/NOPB	Texas Instruments	Active	12	5	30	3	5	0 to 70	8-SOIC
TL061ACDT	STMicroelectronics	Active	3.5	1	30	3	0.2	0 to 70	8-SOIC
TL061CDT	STMicroelectronics	Active	3.5	1	30	3	0.2	0 to 70	8-SOIC
TL061IDT	STMicroelectronics	Active	3.5	1	30	3	0.2	-40 to 105	8-SOIC
TL071ACDT	STMicroelectronics	Active	16	4	20	3	1.4	0 to 70	8-SOIC
TL071CDT	STMicroelectronics	Active	16	4	20	3	1.4	0 to 70	8-SOIC
TL071IDT	STMicroelectronics	Active	16	4	20	3	1.4	-40 to 105	8-SOIC

Engineering Selection Recommendations

Direct Equivalents (Highest Compatibility):

LF351D and LF351DT from STMicroelectronics are direct equivalents of the LF351MX. Both parts share the same base product number (LF351) and maintain J-FET amplifier architecture with single circuit configuration. These devices demonstrate improved electrical performance with higher slew rate (16 V/µs vs. 13 V/µs), lower input bias current (20 pA vs. 50 pA), and reduced supply current (1.4 mA vs. 2.3 mA). Both are classified as Active products with ROHS3 compliance and REACH unaffected status. The primary difference between LF351D and LF351DT is packaging format: LF351D is supplied in Tube, while LF351DT is supplied in Cut Tape and Digi-Reel format.

Functional Alternatives (Electrical Compatibility):

TL071ACDT, TL071CDT, and TL071IDT from STMicroelectronics provide functional substitution with identical electrical specifications to the LF351 series (16 V/µs slew rate, 4 MHz gain bandwidth product, 20 pA input bias current). These devices are based on the TL071 product line and maintain full compatibility with 8-SOIC packaging. TL071IDT extends the operating temperature range to -40°C to 105°C, suitable for industrial applications. All three variants are Active products with ROHS3 compliance.

LF356M/NOPB and LF356MX/NOPB from Texas Instruments represent an alternative with enhanced gain bandwidth product (5 MHz vs. 4 MHz) and improved input bias current (30 pA). These BI-FET series devices operate within the same temperature range and package specification. LF356MX/NOPB offers higher inventory availability (90,234 units) compared to other alternatives.

Lower Performance Alternative:

TL061ACDT, TL061CDT, and TL061IDT are suitable only for applications where reduced slew rate (3.5 V/µs) and lower gain bandwidth product (1 MHz) are acceptable. These devices offer significantly reduced supply current (0.2 mA) and are appropriate for ultra-low-power applications. TL061IDT provides extended temperature range (-40°C to 105°C).

Compliance and Certification:

All substitute parts listed maintain MSL Level 1 (Unlimited) moisture sensitivity rating, REACH unaffected status, and EAR99 ECCN classification, matching the original LF351MX specifications. STMicroelectronics and Texas Instruments substitutes are ROHS3 compliant, exceeding the compliance profile of the obsolete onsemi part.

Frequently Asked Questions (FAQ)

Q: Can LF351D or LF351DT directly replace LF351MX without circuit modification?

A: Yes. LF351D and LF351DT are direct equivalents sharing the same base product number and J-FET architecture. Both maintain the 8-SOIC package footprint compatible with 8-SOP layouts. The improved electrical specifications (higher slew rate, lower input bias current, reduced supply current) are backward compatible with designs specified for LF351MX.

Q: What is the difference between LF351D and LF351DT?

A: Both parts are electrically identical. The difference is packaging format: LF351D is supplied in Tube packaging, while LF351DT is supplied in Cut Tape and Digi-Reel format. Selection depends on assembly process requirements and inventory management preferences.

Q: Are TL071 devices suitable replacements for LF351MX?

A: Yes, with qualification. TL071ACDT, TL071CDT, and TL071IDT provide identical electrical performance to LF351 equivalents (16 V/µs slew rate, 4 MHz gain bandwidth product, 20 pA input bias current). The primary consideration is that TL071 is a different product line; circuit validation is recommended for critical applications, though pin-compatible operation is assured.

Q: Can LF356 series parts replace LF351MX?

A: LF356M/NOPB and LF356MX/NOPB are functionally compatible with enhanced specifications. The 5 MHz gain bandwidth product exceeds LF351MX capability, and 30 pA input bias current is acceptable for most applications. These parts are suitable for designs where improved bandwidth is beneficial or neutral.

Q: Why should TL061 devices not be used as primary substitutes?

A: TL061 series parts (TL061ACDT, TL061CDT, TL061IDT) operate at significantly reduced performance levels: 3.5 V/µs slew rate and 1 MHz gain bandwidth product versus 13 V/µs and 4 MHz for LF351MX. These devices are appropriate only for applications explicitly designed for lower bandwidth and slower slew rate operation. Use TL061 variants only when power consumption reduction (0.2 mA supply current) is a primary design requirement.

Q: What is the significance of operating temperature range differences?

A: LF351MX operates 0°C to 70°C. TL061IDT and TL071IDT extend to -40°C to 105°C, suitable for industrial and automotive applications. For standard commercial temperature range applications, all listed substitutes are acceptable. Extended temperature variants should be selected only when application environment requires operation beyond 0°C to 70°C.

Q: Are all substitute parts RoHS compliant?

A: All STMicroelectronics and Texas Instruments substitutes listed are ROHS3 compliant. The original LF351MX from onsemi does not specify RoHS status. For applications requiring RoHS compliance certification, substitute parts from active manufacturers provide documented compliance.

Q: What packaging considerations apply when substituting LF351MX?

A: LF351MX uses 8-SOP packaging. All substitute parts use 8-SOIC packaging. While both are 8-pin surface mount packages with 0.154" (3.90mm) width, PCB footprint verification is required. 8-SOP and 8-SOIC have identical pin pitch and spacing; however, pad dimensions may differ slightly. Consult manufacturer datasheets and PCB design guidelines to confirm footprint compatibility before production implementation.

Q: Which substitute offers the best inventory availability?

A: LF356MX/NOPB from Texas Instruments provides the highest inventory level at 90,234 units. LF351DT from STMicroelectronics offers 17,545 units. For applications requiring immediate availability and long-term supply assurance, LF356MX/NOPB is the optimal choice.

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