1N751A_T50R Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N751A_T50R is a 5.1 V zener diode rated at 500 mW with ±5% tolerance, manufactured by onsemi in a through-hole DO-35 package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The 1N751A_T50R serves voltage regulation and protection applications requiring precise 5.1 V zener reference characteristics within the specified power and tolerance parameters.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	5.1	V
Tolerance	±5%	—
Power - Max	500	mW
Impedance (Max)	17	Ohms
Current - Reverse Leakage @ Vr	1	µA @ 1 V
Voltage - Forward (Vf) (Max) @ If	1.5	V @ 200 mA
Operating Temperature	-65 to 200	°C
Mounting Type	Through Hole	—
Package / Case	DO-204AH, DO-35, Axial	—

Substitute Part Grouping Explanation

Substitution of the 1N751A_T50R is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 5.1 V (exact match required)
Tolerance: ±5% or tighter (±2% acceptable as upgrade)
Power - Max: 500 mW or greater
Impedance (Max): 17 Ohms or lower (lower impedance preferred)
Operating Temperature: -65°C minimum and 175°C or higher maximum
Mounting Type: Through Hole
Package / Case: DO-35 or DO-204AH compatible

Substitution Categories:

Direct Equivalents maintain identical electrical specifications and package form factor, suitable for direct replacement without circuit redesign.

Parametric Equivalents meet or exceed all critical electrical parameters with minor variations in secondary characteristics such as forward voltage or reverse leakage current.

Similar Parts share the same zener voltage and power rating but may have different impedance or tolerance specifications, requiring application-level verification.

Upgrade Parts provide enhanced performance through tighter tolerance (±2% vs ±5%) or improved temperature range, offering superior regulation characteristics.

Higher Power Alternatives exceed the 500 mW power rating, suitable for applications requiring additional thermal margin or higher current capacity.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (mW)	Zzt (Ohms)	Vf @ 200mA (V)	Temp Range (°C)	Package	Status
1N751A_T50R	onsemi	5.1	±5%	500	17	1.5	-65 to 200	DO-35	Obsolete
1N5231B	Microchip Technology	5.1	±5%	500	17	1.5	-65 to 175	DO-35	Active
1N5231BTR	onsemi	5.1	±5%	500	17	1.2	-65 to 200	DO-35	Active
1N5231CTR	Fairchild Semiconductor	5.1	±2%	500	17	1.1	-65 to 200	DO-35	Active
BZX79C5V1	Taiwan Semiconductor Corporation	5.1	±5%	500	60	1.5	-65 to 175	DO-35	Active
1N751A	Microchip Technology	5.1	±5%	500	17	1.1	-65 to 175	DO-35	Active
1N751A-1	Microchip Technology	5.1	±5%	500	14	1.1	-65 to 175	DO-35	Active
1N751C	Microchip Technology	5.1	±2%	500	17	1.1	-65 to 175	DO-35	Active
1N751C-1	Microchip Technology	5.1	±2%	500	17	1.1	-65 to 175	DO-35	Active
1N751	Microchip Technology	5.1	±10%	400	19	1.1	-65 to 175	DO-35	Active
1N4733A	Lumimax Optoelectronic Technology	5.1	±5%	1000	7	1.2	-65 to 200	DO-41	Active

Engineering Selection Recommendations

Direct Replacement (Preferred):

The 1N5231BTR (onsemi) is the primary direct replacement for the 1N751A_T50R. Both components share identical electrical specifications (5.1 V, ±5%, 500 mW, 17 Ohms impedance) and maintain the full operating temperature range (-65°C to 200°C). The 1N5231BTR is active in production with RoHS3 compliance and REACH unaffected status, ensuring long-term availability and regulatory compliance.

Parametric Equivalent (Enhanced Performance):

The 1N5231CTR (Fairchild Semiconductor) and 1N751C (Microchip Technology) provide tighter tolerance specifications (±2% vs ±5%), resulting in improved voltage regulation accuracy. Both maintain 500 mW power rating and 17 Ohms impedance. The 1N5231CTR extends the operating temperature to 200°C, matching the original specification. These parts are suitable for applications requiring enhanced voltage stability.

Active Production Alternatives:

The 1N751A (Microchip Technology) and 1N751A-1 (Microchip Technology) are active variants of the original part number. The 1N751A-1 offers reduced impedance (14 Ohms vs 17 Ohms), providing lower dynamic resistance. Both are RoHS compliant or non-compliant depending on application requirements. Operating temperature is limited to 175°C.

Higher Power Option:

The 1N4733A (Lumimax Optoelectronic Technology) provides 1 W power dissipation with significantly lower impedance (7 Ohms), suitable for applications requiring enhanced thermal margin or higher current capacity. This part uses a DO-41 package instead of DO-35, requiring physical board layout modification. The 1N4733A maintains the full -65°C to 200°C temperature range.

Not Recommended:

The 1N751 (Microchip Technology) has reduced power rating (400 mW vs 500 mW) and wider tolerance (±10% vs ±5%), making it unsuitable for direct replacement in applications requiring the full 500 mW specification.

The BZX79C5V1 (Taiwan Semiconductor Corporation) exhibits significantly higher impedance (60 Ohms vs 17 Ohms), resulting in degraded voltage regulation performance and is not recommended for direct substitution.

Frequently Asked Questions (FAQ)

Q: Can the 1N5231B replace the 1N751A_T50R?

A: The 1N5231B is electrically equivalent with matching 5.1 V, ±5%, 500 mW, and 17 Ohms specifications. However, the operating temperature range is limited to -65°C to 175°C, compared to the original -65°C to 200°C. Use this part only if the application does not require operation above 175°C.

Q: What is the difference between 1N751C and 1N751C-1?

A: Both parts are identical in electrical specifications and performance. The designation difference reflects manufacturing or packaging variations. Both provide ±2% tolerance and 500 mW power rating with 17 Ohms impedance.

Q: Why does the BZX79C5V1 have higher impedance?

A: The BZX79C5V1 exhibits 60 Ohms maximum impedance compared to 17 Ohms in the 1N751A_T50R. This higher impedance results in greater voltage variation under load changes and is not suitable for applications requiring stable voltage regulation.

Q: Is the 1N4733A a direct replacement?

A: The 1N4733A is not a direct replacement due to package differences (DO-41 vs DO-35). However, it provides superior electrical performance with 1 W power rating and 7 Ohms impedance. Physical board layout modification is required for implementation.

Q: What does ±2% tolerance mean compared to ±5%?

A: ±2% tolerance (1N751C, 1N5231CTR) provides tighter voltage regulation accuracy. For a 5.1 V zener, ±2% tolerance limits variation to ±0.102 V, while ±5% tolerance allows ±0.255 V variation. Tighter tolerance improves voltage stability in precision applications.

Q: Can I use 1N751 as a substitute?

A: The 1N751 is not recommended. It has reduced power rating (400 mW vs 500 mW) and wider tolerance (±10% vs ±5%), making it unsuitable for applications requiring the full 500 mW specification and ±5% accuracy.

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

A: The original 1N751A_T50R operates to 200°C. Substitutes with 175°C maximum temperature limit are suitable only for applications not requiring operation above 175°C. The 1N5231BTR and 1N5231CTR maintain the full 200°C specification.

Q: Are all substitute parts RoHS compliant?

A: RoHS compliance varies by manufacturer and part variant. The 1N5231BTR, 1N5231CTR, 1N751C, and 1N4733A are RoHS3 compliant. The 1N5231B and 1N751A-1 are RoHS non-compliant. Verify compliance requirements for your application.

Q: What does impedance (Zzt) affect in circuit performance?

A: Impedance determines the dynamic resistance of the zener diode under load changes. Lower impedance (7 Ohms in 1N4733A) provides better voltage regulation with smaller voltage variations. Higher impedance (60 Ohms in BZX79C5V1) results in greater voltage ripple and is unsuitable for precision regulation.

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