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

onsemi 1N975B_T50A

Name: 1N975B_T50A
Brand: onsemi
SKU: 1N975B_T50A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N975B_T50A

Manufacturer:: onsemi

Category:: Single Zener Diodes

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

Datasheet:: 1N975B_T50A.pdf

Description:: DIODE ZENER 39V 500MW DO35

Quantity:: RFQ Add To RFQ list

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Inventory:5,937

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Product details

Overview

1N975B_T50A from Fairchild Semiconductor is a 39 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 1N975B_T50A datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage accuracy (37.05–40.95 V), dynamic impedance (7.8 Ω at 5 mA), low leakage current (≤0.25 μA at 31.6 V), and thermal stability across –65°C to +200°C operating range.

Technical Context

This device operates as a two-terminal voltage reference with sharp reverse-breakdown characteristics, specified at I_Z = 5 mA. Its zener voltage exhibits minimal temperature coefficient near zero crossing in the 30–40 V range, supporting stable DC biasing in analog front-ends and sensor excitation circuits.

The DO-35 glass package provides hermetic sealing and high reliability under thermal cycling stress. Power dissipation is rated at 500 mW up to 75°C, derating linearly at 4.0 mW/°C above that temperature, enabling predictable thermal design in compact PCB layouts.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	37.05 V (min) to 40.95 V (max) at I_Z = 5 mA - defines regulated output voltage window for feedback or clamping
Zener Impedance (Z_Z)	7.8 Ω at I_Z = 5 mA - determines load regulation error and AC ripple rejection capability
Maximum Power Dissipation	500 mW at T_L ≤ 75°C - sets maximum continuous DC power handling without thermal runaway
Reverse Leakage Current (I_R)	≤0.25 μA at V_R = 31.6 V - ensures negligible current draw in standby or high-impedance sensing nodes
Operating Temperature Range	–65°C to +200°C - supports deployment in automotive engine compartments and industrial motor drives
Tolerance	±5% - enables use in applications requiring moderate voltage accuracy without trimming

Pinout & Package

DO-35 glass axial package with cathode band marking; 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 or lower potential side in reverse-biased regulation configuration
Cathode	Zener breakdown terminal / Regulated output node	Connected to input voltage source through series resistor; delivers stable 39 V reference when reverse-biased

Key Features

Feature	Design Value
Hermetically sealed DO-35 glass package	Enables long-term parameter stability and moisture resistance in harsh environments
Low dynamic impedance (7.8 Ω)	Minimizes output voltage variation under changing load currents in feedback networks
High-temperature operation (up to +200°C)	Permits placement near heat-generating components without derating penalties
5% voltage tolerance with tight binning	Reduces need for external calibration in cost-sensitive industrial control modules

Applications

Switch-Mode Power Supply Feedback	Overvoltage Protection Clamp
Use Scenario: Used in TL431-based secondary-side feedback loop of isolated AC/DC adapters to regulate 12 V output. IC Role / Device Role / Timing Role: Provides precise 39 V reference to set optocoupler LED current threshold. Use Value: Enables ±1% output regulation accuracy despite line/load variations due to stable V_Z and low Z_Z.	Use Scenario: Placed across DC bus of motor drive inverter to limit transient spikes during IGBT switching. IC Role / Device Role / Timing Role: Acts as passive crowbar element absorbing energy above 40.95 V. Use Value: Prevents gate driver IC damage by clamping transients within safe voltage margin before TVS activation.
Sensor Excitation Reference	Analog Signal Conditioning
Use Scenario: Supplies stable bias voltage to bridge-type pressure sensor in HVAC differential pressure transmitter. IC Role / Device Role / Timing Role: Serves as low-noise, temperature-stable excitation source for Wheatstone bridge. Use Value: Maintains <0.05% full-scale error drift over –40°C to +125°C ambient due to matched TC behavior in 39 V range.	Use Scenario: Sets reference level for comparator input in battery state-of-charge monitor. IC Role / Device Role / Timing Role: Defines trip point for low-voltage warning at 3.3 V system rail via resistive divider. Use Value: Ensures consistent threshold detection across production units thanks to ±5% V_Z tolerance and low IR leakage.

Switch-Mode Power Supply Feedback

Overvoltage Protection Clamp

Use Scenario: Used in TL431-based secondary-side feedback loop of isolated AC/DC adapters to regulate 12 V output.

IC Role / Device Role / Timing Role: Provides precise 39 V reference to set optocoupler LED current threshold.

Use Value: Enables ±1% output regulation accuracy despite line/load variations due to stable V_Z and low Z_Z.

Use Scenario: Placed across DC bus of motor drive inverter to limit transient spikes during IGBT switching.

IC Role / Device Role / Timing Role: Acts as passive crowbar element absorbing energy above 40.95 V.

Use Value: Prevents gate driver IC damage by clamping transients within safe voltage margin before TVS activation.

Sensor Excitation Reference

Analog Signal Conditioning

Use Scenario: Supplies stable bias voltage to bridge-type pressure sensor in HVAC differential pressure transmitter.

IC Role / Device Role / Timing Role: Serves as low-noise, temperature-stable excitation source for Wheatstone bridge.

Use Value: Maintains <0.05% full-scale error drift over –40°C to +125°C ambient due to matched TC behavior in 39 V range.

Use Scenario: Sets reference level for comparator input in battery state-of-charge monitor.

IC Role / Device Role / Timing Role: Defines trip point for low-voltage warning at 3.3 V system rail via resistive divider.

Use Value: Ensures consistent threshold detection across production units thanks to ±5% V_Z tolerance and low IR leakage.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4739A	39 V nominal, ±5%, 1 W rating, DO-41 package - higher power but larger footprint	Preferred where >500 mW dissipation required; less suitable for space-constrained DO-35 layouts	Select when thermal margin exceeds 500 mW or board real estate allows DO-41
BZX55-C39	39 V nominal, ±5%, 500 mW, DO-35 - same package but tighter V_Z distribution (±2% option available)	Better suited for high-precision references where tighter initial tolerance is critical	Choose when ±2% V_Z variants are acceptable and sourcing flexibility favors ON Semiconductor

Compared with 1N975B_T50A, 1N4739A offers higher power headroom at the cost of board area, while BZX55-C39 matches the DO-35 form factor but provides optional tighter voltage tolerance-making it preferable for metrology-grade references where initial accuracy outweighs legacy compatibility.

Availability

1N975B_T50A is available at Aetrix Electronics and suitable for switch-mode power supplies, overvoltage protection circuits, and sensor excitation systems requiring stable component supply with traceable lot history and extended lifecycle support.

Supply support for 1N975B_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 family was developed for general-purpose precision voltage regulation in industrial, computing, and consumer power systems, emphasizing reliability, wide temperature operation, and DO-35 compatibility with legacy designs.

FAQ

What is the nominal zener voltage of the 1N975B_T50A?

The nominal zener voltage of the 1N975B_T50A is 39 V, with a guaranteed range of 37.05 V (minimum) to 40.95 V (maximum) measured at 5 mA test current and 25°C junction temperature. This value reflects the center of the ±5% tolerance band defined in the Fairchild 1N957B–1N979B datasheet Rev. F1.

Does the 1N975B_T50A have a specified zener impedance?

Yes, the 1N975B_T50A has a specified zener impedance (Z_Z) of 7.8 Ω, measured at I_Z = 5 mA and 60 Hz AC signal superimposed on DC bias. This low dynamic impedance ensures minimal output voltage variation under changing load conditions in regulation applications.

What is the maximum power dissipation rating for the 1N975B_T50A?

The 1N975B_T50A is rated for 500 mW maximum power dissipation at lead temperature (T_L) ≤ 75°C with 3/8″ lead length. Above 75°C, it derates linearly at 4.0 mW/°C, reaching zero dissipation at approximately 200°C lead temperature.

Is the 1N975B_T50A suitable for high-temperature environments?

Yes, the 1N975B_T50A supports an operating and storage temperature range of –65°C to +200°C. Its DO-35 glass package and silicon die construction enable reliable operation in under-hood automotive, downhole oil/gas, and industrial motor control applications where ambient temperatures exceed 125°C.

How is the cathode identified on the 1N975B_T50A package?

The cathode of the 1N975B_T50A is marked by a distinct color band on the DO-35 glass body, as stated in the Fairchild datasheet. This band aligns with industry-standard polarity marking for axial-leaded Zener diodes and must be oriented toward the higher potential side in reverse-bias regulation configurations.

1N975B_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):: 39 V

Tolerance:: ±5%

Power - Max:: 500 mW

Impedance (Max) (Zzt):: 80 Ohms

Current - Reverse Leakage @ Vr:: 5 µA @ 29.7 V

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

Operating Temperature:: -65°C ~ 200°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-35

1N975B_T50A FAQ

1.How can I place an order for 1N975B_T50A through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N975B_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 1N975B_T50A reliable?

The price and inventory of 1N975B_T50A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N975B_T50A is usually 5 days.

3.What payment methods are accepted for 1N975B_T50A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N975B_T50A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N975B_T50A?

1N975B_T50A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N975B_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 1N975B_T50A?

For technical support, including 1N975B_T50A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N975B_T50A requirements.

6.How does Aetrix verify that 1N975B_T50A is sourced from the original manufacturer or authorized distributors?

All 1N975B_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 1N975B_T50A meets industry standards.

7.What is the process for return or replacement of 1N975B_T50A?

All 1N975B_T50A units undergo pre-shipment inspection (PSI). If there is an issue with 1N975B_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 1N975B_T50A part is unused and in its original packaging.

Return procedure for 1N975B_T50A:

1.Submit a request within 90 days.

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

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