1N972B_T50A Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N972B_T50A is a 30 V, 500 mW Zener diode manufactured by onsemi in DO-35 axial through-hole packaging. This component is classified as obsolete, necessitating identification of active equivalent and substitute parts for ongoing design requirements and procurement needs. The part operates across a temperature range of -65°C to 200°C with ±5% voltage tolerance and is suitable for voltage regulation and protection applications in electronic circuits.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	30	V
Power - Max	500	mW
Tolerance	±5%	—
Impedance (Max)	49	Ohms
Current - Reverse Leakage @ Vr	5	µA @ 22.8 V
Operating Temperature Range	-65 to 200	°C
Mounting Type	Through Hole	—
Package / Case	DO-35 (DO-204AH)	—

Substitute Part Grouping Explanation

Substitution of the 1N972B_T50A is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 30 V (exact match required)
Tolerance: ±5% (acceptable tolerance band)
Mounting Type: Through Hole (axial configuration)
Operating Temperature Range: Must encompass or exceed -65°C to 200°C

Secondary Compatibility Factors:

Power - Max: 500 mW or higher (uprating acceptable)
Impedance (Max): 49 Ohms or lower (lower impedance acceptable)
Current - Reverse Leakage: 5 µA or lower (lower leakage acceptable)
Package / Case: DO-35, DO-41, or equivalent axial through-hole packages

Substitute parts are grouped into three categories based on power dissipation capability: 500 mW (direct replacement), 1.0–1.5 W (moderate uprating), and 3 W (significant uprating). Package variations (DO-35, DO-7, DO-41) are acceptable provided mechanical fit and thermal characteristics remain compatible with the application circuit.

Parameter Comparison

Part Number	Manufacturer	Vz (Nom)	Tolerance	Power (Max)	Zzt (Max)	Ir @ Vr	Temp Range	Package	Status
1N972B_T50A	onsemi	30 V	±5%	500 mW	49 Ω	5 µA @ 22.8 V	-65 to 200°C	DO-35	Obsolete
1N972B-1	Microchip Technology	27 V	±5%	500 mW	49 Ω	500 nA @ 21 V	-65 to 175°C	DO-35	Active
1N972A	Microchip Technology	30 V	±10%	500 mW	49 Ω	5 µA @ 22.8 V	-65 to 175°C	DO-7	Active
1N972BE3	Microchip Technology	30 V	±5%	500 mW	49 Ω	5 µA @ 22.8 V	-65 to 175°C	DO-7	Active
1N5936BP-TP	Micro Commercial Co	30 V	±5%	1.5 W	28 Ω	1 µA @ 22.8 V	-55 to 175°C	DO-41	Active
1EZ30D5-TP	Micro Commercial Co	30 V	±5%	1 W	40 Ω	5 µA @ 22.5 V	-55 to 150°C	DO-41	Active
1N5936B3P-TP	Micro Commercial Co	30 V	±5%	3 W	28 Ω	1 µA @ 22.8 V	-55 to 175°C	DO-41	Active
1N5077	Microchip Technology	30 V	±5%	3 W	15 Ω	1 µA @ 22.8 V	-65 to 175°C	Axial	Active

Engineering Selection Recommendations

Direct Replacement (500 mW, 30 V, ±5%):

1N972BE3 (Microchip Technology) is the primary direct replacement. It maintains identical electrical specifications (30 V nominal, 500 mW power, ±5% tolerance, 49 Ω impedance, 5 µA reverse leakage) and operates across -65°C to 175°C. The package transitions from DO-35 to DO-7, both axial through-hole configurations with compatible mechanical footprints. Product status is active with full compliance certifications.

Alternative Direct Replacement (500 mW, 30 V, ±10% Tolerance):

1N972A (Microchip Technology) provides equivalent power and voltage specifications with relaxed tolerance (±10% versus ±5%). Operating temperature range is -65°C to 175°C. Package is DO-7 axial. This option is suitable for applications where ±10% voltage tolerance is acceptable. Product status is active.

Voltage Variant (500 mW, 27 V, ±5%):

1N972B-1 (Microchip Technology) is listed in the original substitute list but operates at 27 V nominal instead of 30 V. This part is not recommended as a direct substitute due to voltage mismatch. Use only if circuit design permits 27 V operation.

Uprated Replacements (1.0–1.5 W, 30 V, ±5%):

1N5936BP-TP (Micro Commercial Co) provides 1.5 W power dissipation with 30 V nominal voltage and ±5% tolerance. Operating temperature is -55°C to 175°C. Package is DO-41 axial. Lower impedance (28 Ω) and reduced reverse leakage (1 µA) improve performance. Product status is active with RoHS3 compliance.

1EZ30D5-TP (Micro Commercial Co) provides 1 W power dissipation with 30 V nominal voltage and ±5% tolerance. Operating temperature is -55°C to 150°C. Package is DO-41 axial. Product status is active. Note: Operating temperature maximum is 150°C, which is lower than the original part specification.

High-Power Replacement (3 W, 30 V, ±5%):

1N5077 (Microchip Technology) provides 3 W power dissipation with 30 V nominal voltage and ±5% tolerance. Operating temperature is -65°C to 175°C, matching the original lower temperature limit. Impedance is significantly lower (15 Ω), providing superior voltage regulation. Package is axial through-hole. Product status is active.

1N5936B3P-TP (Micro Commercial Co) provides 3 W power dissipation with 30 V nominal voltage and ±5% tolerance. Operating temperature is -55°C to 175°C. Package is DO-41 axial. Impedance is 28 Ω. Product status is active.

Selection Basis:

For applications requiring exact thermal performance match: 1N972BE3 or 1N5077
For applications permitting relaxed tolerance: 1N972A
For applications requiring higher power dissipation: 1N5936BP-TP, 1EZ30D5-TP, 1N5936B3P-TP, or 1N5077
For applications with strict lower temperature limit (-65°C): 1N972BE3, 1N972A, or 1N5077

Frequently Asked Questions (FAQ)

Q: Can 1N972BE3 directly replace 1N972B_T50A in existing circuit boards?

A: 1N972BE3 maintains identical electrical specifications (30 V, 500 mW, ±5%, 49 Ω impedance). Both are axial through-hole packages. The transition from DO-35 to DO-7 package requires verification of mechanical fit within the PCB layout, as DO-7 has slightly different lead spacing. Electrical performance is equivalent.

Q: What is the difference between 1N972A and 1N972BE3?

A: Both are 30 V, 500 mW Zener diodes from Microchip Technology in axial through-hole packages. The primary difference is tolerance: 1N972A has ±10% tolerance while 1N972BE3 has ±5% tolerance. Select 1N972BE3 for applications requiring tighter voltage regulation. Both operate from -65°C to 175°C.

Q: Why do some substitutes have higher power ratings (1 W, 1.5 W, 3 W)?

A: Higher power ratings provide increased thermal margin and improved voltage regulation characteristics. These parts can dissipate more heat without exceeding maximum junction temperature. They are suitable replacements when the original 500 mW rating is insufficient or when improved performance is desired. Mechanical package changes (DO-35 to DO-41) may require PCB layout verification.

Q: Is 1N972B-1 a suitable replacement?

A: 1N972B-1 operates at 27 V nominal voltage instead of 30 V. This voltage mismatch makes it unsuitable as a direct replacement unless the circuit design is modified to accept 27 V operation. Do not use this part for 30 V applications.

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

A: The original 1N972B_T50A operates from -65°C to 200°C. Most active substitutes operate to 175°C maximum. For applications requiring operation above 175°C, verify that the substitute part's thermal specifications remain within acceptable limits. 1N5077 and 1N972BE3 maintain the -65°C lower limit, ensuring cold-temperature performance equivalence.

Q: Can I use 1EZ30D5-TP if my application operates below -55°C?

A: No. 1EZ30D5-TP has a minimum operating temperature of -55°C. The original part operates to -65°C. For applications requiring -65°C operation, select 1N972BE3, 1N972A, or 1N5077.

Q: What does impedance (Zzt) mean in Zener diode selection?

A: Impedance (Zzt) represents the dynamic resistance of the Zener diode in the reverse-bias region. Lower impedance provides better voltage regulation and faster response to load changes. Substitutes with lower impedance (e.g., 1N5077 at 15 Ω) offer improved performance compared to the original 49 Ω specification.

Q: Are all substitute parts RoHS compliant?

A: Compliance information varies. 1N5936BP-TP is explicitly RoHS3 compliant. Other parts are REACH unaffected. Verify specific compliance requirements for your application and procurement standards before final selection.

Q: What is the significance of reverse leakage current differences?

A: Reverse leakage current (Ir) indicates the small current flowing through the Zener diode when reverse-biased below the Zener voltage. Lower leakage (e.g., 1 µA versus 5 µA) reduces power consumption in standby conditions and improves circuit efficiency. This is particularly important in low-power applications.

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