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

onsemi 1N973B_T50R

Name: 1N973B_T50R
Brand: onsemi
SKU: 1N973B_T50R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N973B_T50R

Manufacturer:: onsemi

Category:: Single Zener Diodes

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

Datasheet:: 1N973B_T50R.pdf

Description:: DIODE ZENER 33V 500MW DO35

Quantity:: RFQ Add To RFQ list

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Inventory:7,551

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Product details

Overview

1N973B_T50R from Fairchild Semiconductor is a 33 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 1N973B_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance (±5%), dynamic impedance (9.2 Ω at 5 mA), maximum reverse leakage (0.25 μA at 25.1 V), and thermal derating (4.0 mW/°C above 75°C).

Technical Context

The 1N973B_T50R operates as a two-terminal voltage reference device with sharp reverse breakdown characteristics. Its zener voltage is specified at 31.35 V (min), 33 V (typ), and 34.65 V (max) under 5 mA test current, with low dynamic impedance of 9.2 Ω ensuring stable regulation across load variations.

It features a DO-35 glass axial package rated for -65°C to +200°C operating temperature, with 500 mW power dissipation at TL ≤ 75°C and linear derating beyond that point. Reverse leakage remains ≤0.25 μA up to 25.1 V, supporting low-power biasing and high-impedance sensing roles.

Key Specifications

Parameter	Value and Actual Design Meaning
Zener Voltage (V_Z)	31.35–34.65 V at 5 mA - defines precise clamping/reference level in feedback or protection circuits
Zener Impedance (Z_Z)	9.2 Ω at 5 mA - ensures minimal output voltage variation under changing load current
Power Dissipation (P_D)	500 mW @ T_L ≤ 75°C - sets maximum continuous power handling in linear regulator or shunt reference use
Reverse Leakage (I_R)	≤0.25 μA @ 25.1 V - enables ultra-low standby current in battery-backed or high-impedance monitoring paths
Operating Temp Range	-65°C to +200°C - supports deployment in automotive under-hood, industrial motor control, and aerospace environments
Tolerance	±5% - provides predictable voltage accuracy without trimming in cost-sensitive designs
Package	DO-35 glass axial - offers hermetic sealing, high reliability, and compatibility with through-hole wave soldering

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; two-terminal device requiring no external biasing or control signals.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Current entry terminal in forward bias; common reference node in reverse-biased regulation	Connected to lower-potential side of circuit; forms return path for zener current in shunt configuration
Cathode	Current exit terminal in forward bias; regulated output node in reverse bias	Marked with color band; connected to voltage node requiring stabilization or clamping

Key Features

Feature	Design Value
Stable 33 V reference	Guaranteed 31.35–34.65 V range at 5 mA enables accurate feedback in SMPS and LDO error amplifiers
Low dynamic impedance	9.2 Ω maintains <10 mV output shift per 1 mA load change-critical for precision analog references
Hermetic DO-35 package	Glass-sealed construction ensures long-term parameter stability and resistance to moisture/humidity degradation
Wide temperature operation	-65°C to +200°C rating supports use in engine control units, downhole tools, and military-grade power systems
5% voltage tolerance	Eliminates need for post-assembly calibration in cost-driven consumer and industrial power supplies

Applications

Switch-Mode Power Supply Feedback	Overvoltage Protection Clamp
Use Scenario: Used in optocoupler-coupled feedback loop of isolated flyback converter to regulate 12 V output. IC Role / Device Role / Timing Role: Zener reference providing stable 33 V threshold to TL431 cathode bias network. Use Value: Enables ±1% output regulation via tight V_Z tolerance and low Z_Z, reducing need for secondary-side trimming.	Use Scenario: Placed across DC bus of 24 V industrial PLC input module to suppress transients >35 V. IC Role / Device Role / Timing Role: Shunt clamp limiting voltage excursion during ESD or inductive kick events. Use Value: Sub-μA leakage preserves high-impedance input integrity; 500 mW rating handles 100 ms surge pulses without degradation.
Analog Sensor Signal Conditioning	Reference Voltage Source for ADC
Use Scenario: Biasing thermistor bridge in HVAC temperature sensor to establish 33 V reference rail for differential amplifier. IC Role / Device Role / Timing Role: Precision voltage source setting common-mode level and gain scaling factor. Use Value: Low tempco and 9.2 Ω Z_Z minimize drift-induced measurement error across -40°C to +85°C ambient.	Use Scenario: Providing stable reference to 12-bit SAR ADC in data acquisition front-end for motor current sensing. IC Role / Device Role / Timing Role: External V_REF source replacing internal bandgap to improve INL/DNL performance. Use Value: ±5% initial accuracy and <0.25 μA leakage prevent reference loading errors and enable ratiometric conversion stability.

Switch-Mode Power Supply Feedback

Overvoltage Protection Clamp

Use Scenario: Used in optocoupler-coupled feedback loop of isolated flyback converter to regulate 12 V output.

IC Role / Device Role / Timing Role: Zener reference providing stable 33 V threshold to TL431 cathode bias network.

Use Value: Enables ±1% output regulation via tight V_Z tolerance and low Z_Z, reducing need for secondary-side trimming.

Use Scenario: Placed across DC bus of 24 V industrial PLC input module to suppress transients >35 V.

IC Role / Device Role / Timing Role: Shunt clamp limiting voltage excursion during ESD or inductive kick events.

Use Value: Sub-μA leakage preserves high-impedance input integrity; 500 mW rating handles 100 ms surge pulses without degradation.

Analog Sensor Signal Conditioning

Reference Voltage Source for ADC

Use Scenario: Biasing thermistor bridge in HVAC temperature sensor to establish 33 V reference rail for differential amplifier.

IC Role / Device Role / Timing Role: Precision voltage source setting common-mode level and gain scaling factor.

Use Value: Low tempco and 9.2 Ω Z_Z minimize drift-induced measurement error across -40°C to +85°C ambient.

Use Scenario: Providing stable reference to 12-bit SAR ADC in data acquisition front-end for motor current sensing.

IC Role / Device Role / Timing Role: External V_REF source replacing internal bandgap to improve INL/DNL performance.

Use Value: ±5% initial accuracy and <0.25 μA leakage prevent reference loading errors and enable ratiometric conversion stability.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4749A	33 V nominal, ±5%, 1 W power rating, DO-41 package	Higher power handling but larger footprint; less suitable for space-constrained PCBs	Choose when >500 mW dissipation is required and board area permits DO-41 layout
BZX55C33	33 V nominal, ±5%, 500 mW, DO-35 package, tighter tempco (±0.05%/°C vs unspecified for 1N973B_T50R)	Better temperature stability but higher unit cost and limited legacy availability	Prefer for new designs demanding improved thermal drift performance where cost is secondary

Compared with 1N4749A and BZX55C33, the 1N973B_T50R offers identical voltage rating and tolerance in the compact DO-35 form factor, with proven field reliability in legacy industrial systems-making it optimal for drop-in replacement in existing DO-35 footprints where 500 mW suffices.

Availability

1N973B_T50R is available at Aetrix Electronics and suitable for switch-mode power supplies, overvoltage protection circuits, and analog sensor signal conditioning requiring stable component supply and long-lifecycle support.

Supply support for 1N973B_T50R 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 series was developed as a standard family of general-purpose Zener diodes for voltage regulation, reference, and protection in industrial, computing, and consumer power systems.

FAQ

What is the nominal zener voltage of the 1N973B_T50R?

The 1N973B_T50R has a nominal zener voltage of 33 V, with a guaranteed range of 31.35 V (minimum) to 34.65 V (maximum) when tested at 5 mA current and 25°C junction temperature. This specification is defined in the Fairchild 1N957B–1N979B datasheet Rev. F1 and applies directly to the 1N973B_T50R variant.

What package type does the 1N973B_T50R use?

The 1N973B_T50R uses the DO-35 glass axial package, identified by a cathode color band and standardized lead spacing. This hermetically sealed package supports through-hole mounting and is explicitly confirmed in the "Top Mark Information" section and mechanical drawings of the Fairchild 1N957B–1N979B datasheet.

What is the maximum power dissipation for the 1N973B_T50R?

The 1N973B_T50R has a maximum power dissipation of 500 mW at lead temperature (T_L) ≤ 75°C with 3/8″ lead length. It derates linearly at 4.0 mW/°C above 75°C, as specified in the Absolute Maximum Ratings table of the official Fairchild datasheet.

What is the zener impedance of the 1N973B_T50R at 5 mA?

The zener impedance (Z_Z) of the 1N973B_T50R is 9.2 Ω at 5 mA test current, measured using 60 Hz AC signal with I_Z(ac) = 0.1 × I_Z(dc). This value reflects the device's ability to maintain stable voltage under small-signal load variations and is documented in the Electrical Characteristics table for the 1N973B row.

Is the 1N973B_T50R suitable for high-temperature environments?

Yes, the 1N973B_T50R is rated for operation from -65°C to +200°C, making it suitable for under-hood automotive, industrial motor drives, and downhole instrumentation. Its DO-35 glass package and silicon die construction provide proven reliability across this full range, as stated in the Absolute Maximum Ratings section of the Fairchild datasheet.

1N973B_T50R Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Voltage - Zener (Nom) (Vz):: 33 V

Tolerance:: ±5%

Power - Max:: 500 mW

Impedance (Max) (Zzt):: 58 Ohms

Current - Reverse Leakage @ Vr:: 5 µA @ 25.1 V

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

Operating Temperature:: -65°C ~ 200°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-35

1N973B_T50R FAQ

1.How can I place an order for 1N973B_T50R through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N973B_T50R 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 1N973B_T50R reliable?

The price and inventory of 1N973B_T50R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N973B_T50R is usually 5 days.

3.What payment methods are accepted for 1N973B_T50R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N973B_T50R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N973B_T50R?

1N973B_T50R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N973B_T50R 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 1N973B_T50R?

For technical support, including 1N973B_T50R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N973B_T50R requirements.

6.How does Aetrix verify that 1N973B_T50R is sourced from the original manufacturer or authorized distributors?

All 1N973B_T50R 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 1N973B_T50R meets industry standards.

7.What is the process for return or replacement of 1N973B_T50R?

All 1N973B_T50R units undergo pre-shipment inspection (PSI). If there is an issue with 1N973B_T50R, 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 1N973B_T50R part is unused and in its original packaging.

Return procedure for 1N973B_T50R:

1.Submit a request within 90 days.

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

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