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

onsemi 1N975B

Name: 1N975B
Brand: onsemi
SKU: 1N975B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N975B

Manufacturer:: onsemi

Category:: Single Zener Diodes

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

Datasheet:: 1N975B.pdf

Description:: DIODE ZENER 39V 500MW DO35

Quantity:: RFQ Add To RFQ list

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Inventory:7,765

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Product details

Overview

1N975B 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 datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage accuracy (37.05–40.95 V), dynamic impedance (7.8 Ω @ 32 mA), low leakage current (0.25 μA @ 31.6 V), and thermal stability across –65°C to +200°C operating range.

Technical Context

The 1N975B operates as a reverse-biased silicon junction device with tightly controlled breakdown characteristics. Its zener voltage is specified at I_Z = 32 mA, with typical dynamic impedance of 7.8 Ω and knee impedance (Z_ZK) of 1000 Ω at I_ZK = 5 mA.

It features a DO-35 axial glass package with cathode band marking, rated for 500 mW power dissipation at T_L ≤ 75°C and derated at 4.0 mW/°C above that temperature. The device meets MIL-STD-19500/207 and JANTXV reliability screening levels per datasheet Rev. F1.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	37.05 V (min) to 40.95 V (max) at I_Z = 32 mA - defines stable regulation window for feedback or clamp circuits
Power Dissipation (P_D)	500 mW @ T_L ≤ 75°C - sets maximum continuous DC power handling in lead-mounted configuration
Zener Impedance (Z_Z)	7.8 Ω @ I_Z = 32 mA - determines output voltage variation under load transients
Reverse Leakage (I_R)	0.25 μA @ V_R = 31.6 V - ensures minimal error current in high-impedance reference nodes
Operating Temp Range	–65°C to +200°C - supports operation in automotive under-hood, industrial control, and aerospace environments
Tolerance	±5% - enables predictable voltage setting without post-calibration in cost-sensitive designs

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; leads are tinned copper alloy, suitable for through-hole soldering. No polarity reversal or dual-anode variants exist for this part.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward conduction terminal / Reference ground node	Connected to circuit common when used in shunt regulation; must sink full load current during overvoltage events
Cathode	Zener breakdown terminal / Regulated output node	Provides stable voltage referenced to anode; marked by visible band on glass body

Key Features

Feature	Design Value
Precision voltage reference	39 V nominal ±5% tolerance ensures consistent setpoint across production lots without trimming
Low dynamic impedance	7.8 Ω at 32 mA enables <10 mV output shift under 10 mA load step - critical for stable feedback loops
High-temperature capability	Rated up to +200°C junction temperature - supports use in sealed enclosures or near heat sources
Hermetic glass package	DO-35 construction provides moisture resistance and long-term parameter stability vs. plastic alternatives

Applications

Switch-Mode Power Supply Feedback	Industrial Sensor Signal Conditioning
Use Scenario: Used in optocoupler-coupled secondary-side feedback path of isolated DC-DC converters. IC Role / Device Role / Timing Role: Provides precise 39 V reference for TL431-like comparator function in voltage-sense loop. Use Value: Enables ±1% output regulation accuracy despite input line and load variations.	Use Scenario: Biasing and clamping analog front-end inputs in 4–20 mA transmitter modules. IC Role / Device Role / Timing Role: Acts as overvoltage protector and level-shifter for op-amp input stages. Use Value: Prevents ADC saturation during ESD or surge events while maintaining signal fidelity below 39 V.
Automotive Battery Monitoring	Programmable Logic Controller Input Protection
Use Scenario: Voltage threshold detection in 24 V vehicle battery health monitoring circuits. IC Role / Device Role / Timing Role: Shunt regulator establishing known trip point for microcontroller ADC sampling. Use Value: Delivers repeatable 39 V trigger with <±0.5 V drift over –40°C to +125°C ambient.	Use Scenario: Input stage protection on digital I/O cards exposed to field wiring transients. IC Role / Device Role / Timing Role: Clamps induced surges to 39 V before reaching FPGA or microcontroller GPIO. Use Value: Limits transient energy to safe levels while preserving logic-level compatibility via series resistor.

Switch-Mode Power Supply Feedback

Industrial Sensor Signal Conditioning

Use Scenario: Used in optocoupler-coupled secondary-side feedback path of isolated DC-DC converters.

IC Role / Device Role / Timing Role: Provides precise 39 V reference for TL431-like comparator function in voltage-sense loop.

Use Value: Enables ±1% output regulation accuracy despite input line and load variations.

Use Scenario: Biasing and clamping analog front-end inputs in 4–20 mA transmitter modules.

IC Role / Device Role / Timing Role: Acts as overvoltage protector and level-shifter for op-amp input stages.

Use Value: Prevents ADC saturation during ESD or surge events while maintaining signal fidelity below 39 V.

Automotive Battery Monitoring

Programmable Logic Controller Input Protection

Use Scenario: Voltage threshold detection in 24 V vehicle battery health monitoring circuits.

IC Role / Device Role / Timing Role: Shunt regulator establishing known trip point for microcontroller ADC sampling.

Use Value: Delivers repeatable 39 V trigger with <±0.5 V drift over –40°C to +125°C ambient.

Use Scenario: Input stage protection on digital I/O cards exposed to field wiring transients.

IC Role / Device Role / Timing Role: Clamps induced surges to 39 V before reaching FPGA or microcontroller GPIO.

Use Value: Limits transient energy to safe levels while preserving logic-level compatibility via series resistor.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4749A	Same nominal voltage (39 V), but ±5% tolerance and 1 W rating in DO-41 package	Higher power handling allows higher current regulation; larger footprint requires PCB redesign	Select when >500 mW dissipation or improved thermal margin is required
BZX55-C39	39 V ±5%, 500 mW, DO-35, but tighter V_Z distribution (±2% option available) and lower Z_Z (5 Ω)	Improved regulation stability in precision references; same footprint enables drop-in replacement	Prefer for metrology-grade references where <5 mV regulation error is mandatory

Compared with 1N4749A and BZX55-C39, the 1N975B offers legacy compatibility, proven reliability in high-temp environments, and identical DO-35 form factor - making it optimal for maintenance of existing designs where thermal robustness and footprint retention are prioritized over ultra-low impedance or higher power.

Availability

1N975B is available at Aetrix Electronics and suitable for switch-mode power supplies, industrial sensor interfaces, automotive battery monitors, and programmable logic controller input protection requiring stable component supply and long-lifecycle support.

Supply support for 1N975B 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 components before its acquisition by ON Semiconductor in 2016.

The 1N957B–1N979B family was developed for general-purpose, high-reliability Zener regulation in industrial and automotive systems where DO-35 packaging and wide temperature operation were essential design requirements.

FAQ

What is the nominal zener voltage of the 1N975B?

The 1N975B has a nominal zener voltage of 39 V, with a guaranteed range of 37.05 V (minimum) to 40.95 V (maximum) at test current I_Z = 32 mA. This value is measured under thermal equilibrium conditions at lead temperature T_L = 30°C ± 1°C with 3/8″ lead length, per Fairchild datasheet Rev. F1.

What is the maximum power dissipation rating for the 1N975B?

The 1N975B is rated for 500 mW power dissipation at lead temperature T_L ≤ 75°C. Above 75°C, it must be derated linearly at 4.0 mW/°C. This rating assumes standard 3/8″ lead length and free-air mounting - actual board-level thermal performance depends on copper area and airflow.

Does the 1N975B have a defined cathode marking?

Yes, the 1N975B uses a DO-35 glass package with a visible cathode band painted on the body. Per Fairchild top-marking specification, the cathode end is unambiguously identified by this band, and the device must be oriented accordingly in circuit layout to ensure proper reverse-bias operation.

What is the zener impedance of the 1N975B at rated current?

The 1N975B exhibits a typical zener impedance (Z_Z) of 7.8 Ω at I_Z = 32 mA, as specified in the Electrical Characteristics table. This value reflects AC impedance derived from small-signal voltage/current ratio at 60 Hz, and directly impacts regulation stability under dynamic load conditions.

Is the 1N975B suitable for high-temperature applications?

Yes, the 1N975B is qualified for operation from –65°C to +200°C, making it suitable for under-hood automotive, downhole instrumentation, and industrial control applications. Its glass-encapsulated DO-35 construction contributes to long-term parameter stability at elevated temperatures, unlike many plastic-packaged Zeners.

1N975B Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Bulk

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 FAQ

1.How can I place an order for 1N975B through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N975B 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 reliable?

The price and inventory of 1N975B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N975B is usually 5 days.

3.What payment methods are accepted for 1N975B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N975B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N975B?

1N975B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N975B 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?

For technical support, including 1N975B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N975B requirements.

6.How does Aetrix verify that 1N975B is sourced from the original manufacturer or authorized distributors?

All 1N975B 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 meets industry standards.

7.What is the process for return or replacement of 1N975B?

All 1N975B units undergo pre-shipment inspection (PSI). If there is an issue with 1N975B, 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 part is unused and in its original packaging.

Return procedure for 1N975B:

1.Submit a request within 90 days.

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

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