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Home > Products > Discrete Semiconductor Products > Diodes > Zener > Single Zener Diodes

onsemi 1N972B_T50A

Name: 1N972B_T50A
Brand: onsemi
SKU: 1N972B_T50A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N972B_T50A

Manufacturer:: onsemi

Category:: Single Zener Diodes

Package:: DO-204AH, DO-35, Axial

Datasheet:: 1N972B_T50A.pdf

Description:: DIODE ZENER 30V 500MW DO35

Quantity:: RFQ Add To RFQ list

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Inventory:4,029

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Product details

Overview

1N972B_T50A from Fairchild Semiconductor is a 30 V, 5% tolerance, 500 mW glass-encapsulated Zener diode in DO-35 package, designed for precision voltage regulation and reference applications in power supply feedback loops, overvoltage protection circuits, and analog signal conditioning stages.

For engineers reviewing the 1N972B_T50A datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage (30 V), zener impedance (4.2 Ω at 49 mA), maximum reverse current (0.25 μA at 22.8 V), power derating (4.0 mW/°C above 75°C), and DO-35 thermal performance limits.

Technical Context

This device operates as a two-terminal voltage reference with stable breakdown behavior under reverse bias. Its 30 V nominal zener voltage is specified at I_Z = 49 mA, with typical zener impedance of 4.2 Ω and knee impedance (ZZK) of 1000 Ω at I_ZK = 5 mA.

The DO-35 glass package supports operation from –65°C to +200°C, with power dissipation rated at 500 mW up to 75°C and linear derating beyond that point. Reverse leakage remains ≤0.25 μA at 22.8 V (80% of V_Z).

Key Specifications

Parameter	Value and Actual Design Meaning
V_Z (Nominal)	30 V - precise DC voltage reference point at 49 mA test current
Tolerance	±5% - ensures V_Z falls between 28.5 V and 31.5 V across production lot
Z_Z @ I_Z	4.2 Ω - low dynamic impedance enables stable regulation under load transients
P_D @ T_L ≤ 75°C	500 mW - maximum continuous power in free-air with 3/8″ lead length
Derating Coefficient	4.0 mW/°C - defines safe power reduction per degree above 75°C ambient
I_R @ V_R = 22.8 V	≤0.25 μA - minimal leakage preserves accuracy in high-impedance bias networks
T_J/T_STG	–65°C to +200°C - wide temperature range supports industrial and under-hood use

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; two-terminal device with no internal connections beyond anode and cathode leads.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward conduction terminal / Reference ground node	Connected to circuit common when used in shunt regulation; defines polarity for reverse-bias operation
Cathode	Zener breakdown terminal / Voltage reference output	Marked with color band; supplies regulated voltage relative to anode in reverse-biased configuration

Key Features

Feature	Design Value
Stable 30 V reference	Guaranteed ±5% tolerance and low tempco enable repeatable setpoints in feedback networks
Low zener impedance	4.2 Ω at 49 mA minimizes output voltage shift under varying load currents
High-temperature capability	Rated to +200°C junction temperature supports under-hood and industrial environments
Low leakage current	≤0.25 μA at 22.8 V reduces error in high-resistance divider or sensing paths
DO-35 glass construction	Hermetic seal and thermal stability ensure long-term parameter consistency

Applications

Switching Power Supply Feedback	Overvoltage Protection Clamp
Use Scenario: Used in TL431-based or discrete op-amp feedback loops to regulate output voltage in AC/DC adapters and DC/DC converters. IC Role / Device Role / Timing Role: Provides precise 30 V reference for error amplifier comparison against scaled output voltage. Use Value: Tight 5% tolerance and low ZZ maintain regulation accuracy within ±1% over line/load variations.	Use Scenario: Placed across sensitive IC inputs or bus lines to clamp transient overvoltages exceeding 30 V. IC Role / Device Role / Timing Role: Acts as passive crowbar element that conducts above V_Z, diverting surge current away from downstream components. Use Value: Fast 60 Hz AC impedance response and 500 mW surge handling limit peak voltage to ≤31.5 V reliably.
Instrumentation Voltage Reference	ADC/DAC Bias Network Stabilization
Use Scenario: Supplies stable bias to op-amps, comparators, or sensor excitation circuits in portable test equipment. IC Role / Device Role / Timing Role: Serves as low-drift, low-noise DC reference source independent of supply rail fluctuations. Use Value: ≤0.25 μA leakage and DO-35 thermal stability reduce offset drift to <10 ppm/°C in precision designs.	Use Scenario: Sets reference voltage for resistor-divider networks feeding ADC input ranges or DAC output scaling. IC Role / Device Role / Timing Role: Anchors analog front-end gain and offset calibration points with known, fixed voltage. Use Value: 4.2 Ω dynamic impedance prevents loading-induced errors when driving 10 kΩ+ divider impedances.

Switching Power Supply Feedback

Overvoltage Protection Clamp

Use Scenario: Used in TL431-based or discrete op-amp feedback loops to regulate output voltage in AC/DC adapters and DC/DC converters.

IC Role / Device Role / Timing Role: Provides precise 30 V reference for error amplifier comparison against scaled output voltage.

Use Value: Tight 5% tolerance and low ZZ maintain regulation accuracy within ±1% over line/load variations.

Use Scenario: Placed across sensitive IC inputs or bus lines to clamp transient overvoltages exceeding 30 V.

IC Role / Device Role / Timing Role: Acts as passive crowbar element that conducts above V_Z, diverting surge current away from downstream components.

Use Value: Fast 60 Hz AC impedance response and 500 mW surge handling limit peak voltage to ≤31.5 V reliably.

Instrumentation Voltage Reference

ADC/DAC Bias Network Stabilization

Use Scenario: Supplies stable bias to op-amps, comparators, or sensor excitation circuits in portable test equipment.

IC Role / Device Role / Timing Role: Serves as low-drift, low-noise DC reference source independent of supply rail fluctuations.

Use Value: ≤0.25 μA leakage and DO-35 thermal stability reduce offset drift to <10 ppm/°C in precision designs.

Use Scenario: Sets reference voltage for resistor-divider networks feeding ADC input ranges or DAC output scaling.

IC Role / Device Role / Timing Role: Anchors analog front-end gain and offset calibration points with known, fixed voltage.

Use Value: 4.2 Ω dynamic impedance prevents loading-induced errors when driving 10 kΩ+ divider impedances.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Zener diode applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4745A	30 V nominal, ±5%, 1 W rating, DO-41 package, higher power but larger footprint	Preferred where >500 mW surge energy must be absorbed without derating	Select 1N4745A when board space allows DO-41 and thermal margin exceeds 500 mW
BZX55C30	30 V nominal, ±5%, 500 mW, DO-35, tighter ZZ spec (max 35 Ω vs. 4.2 Ω typ), lower I_R (≤0.1 μA)	Better suited for ultra-low-leakage bias networks and low-current references	Choose BZX55C30 when sub-0.1 μA leakage is required and 35 Ω max ZZ is acceptable

Compared with 1N972B_T50A, 1N4745A offers higher power handling in a larger package, while BZX55C30 delivers lower leakage and guaranteed max impedance at the cost of typical impedance performance-selection depends on thermal, leakage, and layout constraints.

Availability

1N972B_T50A is available at Aetrix Electronics and suitable for switching power supply feedback, overvoltage protection clamping, and instrumentation voltage reference applications requiring stable component supply and long-lifecycle support.

Supply support for 1N972B_T50A includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The 1N957B–1N979B series was developed for general-purpose, high-reliability Zener regulation in industrial, computing, and consumer power systems where DO-35 form factor and ±5% tolerance met cost-performance targets.

FAQ

What is the nominal zener voltage and tolerance of the 1N972B_T50A?

The 1N972B_T50A has a nominal zener voltage of 30 V with a tolerance of ±5%, meaning its actual breakdown voltage falls between 28.5 V and 31.5 V when measured at 49 mA and 25°C. This tolerance is guaranteed across manufacturing lots and supports predictable design margins in voltage-reference circuits.

What is the maximum power dissipation and derating behavior of the 1N972B_T50A?

The 1N972B_T50A is rated for 500 mW power dissipation at lead temperature ≤75°C with 3/8″ lead length. Above 75°C, it derates linearly at 4.0 mW/°C. This thermal profile allows reliable operation up to +200°C junction temperature when properly heatsinked or mounted with appropriate lead length.

What is the zener impedance of the 1N972B_T50A and why does it matter?

The 1N972B_T50A exhibits a typical zener impedance (Z_Z) of 4.2 Ω at 49 mA. Low impedance ensures minimal output voltage variation under changing load currents-critical for maintaining regulation accuracy in feedback loops and reference networks where stability under dynamic conditions is required.

How is the cathode identified on the 1N972B_T50A DO-35 package?

The cathode of the 1N972B_T50A is marked by a visible color band on the DO-35 glass body. This band must be oriented toward the more positive potential in shunt regulator configurations. The anode is the unmarked lead, and correct polarity is essential to achieve proper reverse-bias zener operation.

What are the storage and operating temperature limits for the 1N972B_T50A?

The 1N972B_T50A supports an operating and storage temperature range of –65°C to +200°C. This wide specification reflects its DO-35 glass encapsulation and makes it suitable for under-hood automotive modules, industrial controls, and aerospace-adjacent applications where extreme thermal cycling occurs.

1N972B_T50A Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: DO-204AH, DO-35, Axial

Packaging:: Tape & Box (TB)

Product Status:: Obsolete

Voltage - Zener (Nom) (Vz):: 30 V

Tolerance:: ±5%

Power - Max:: 500 mW

Impedance (Max) (Zzt):: 49 Ohms

Current - Reverse Leakage @ Vr:: 5 µA @ 22.8 V

Voltage - Forward (Vf) (Max) @ If:: -

Operating Temperature:: -65°C ~ 200°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-35

1N972B_T50A FAQ

1.How can I place an order for 1N972B_T50A through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N972B_T50A on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for 1N972B_T50A reliable?

The price and inventory of 1N972B_T50A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N972B_T50A is usually 5 days.

3.What payment methods are accepted for 1N972B_T50A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N972B_T50A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N972B_T50A?

1N972B_T50A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N972B_T50A order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for 1N972B_T50A?

For technical support, including 1N972B_T50A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N972B_T50A requirements.

6.How does Aetrix verify that 1N972B_T50A is sourced from the original manufacturer or authorized distributors?

All 1N972B_T50A products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 1N972B_T50A meets industry standards.

7.What is the process for return or replacement of 1N972B_T50A?

All 1N972B_T50A units undergo pre-shipment inspection (PSI). If there is an issue with 1N972B_T50A, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The 1N972B_T50A part is unused and in its original packaging.

Return procedure for 1N972B_T50A:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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