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

onsemi 1N748A_T50R

Name: 1N748A_T50R
Brand: onsemi
SKU: 1N748A_T50R
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 1N748A_T50R

Manufacturer:: onsemi

Category:: Single Zener Diodes

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

Datasheet:: 1N748A_T50R.pdf

Description:: DIODE ZENER 3.9V 500MW DO35

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Product details

Overview

1N748A_T50R from Fairchild Semiconductor is a 3.9 V ±5% silicon Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C, with 23 Ω dynamic impedance at 20 mA and 95 mA maximum Zener current, used for precision voltage reference and overvoltage protection in low-power analog circuits.

For engineers reviewing the 1N748A_T50R datasheet, pinout, applications, or equivalent options, key selection criteria include nominal Zener voltage (3.9 V), tolerance (±5%), dynamic impedance (23 Ω), power rating (500 mW), and DO-35 thermal derating behavior (4.0 mW/°C above 75°C).

Technical Context

This device operates as a reverse-biased voltage-regulating diode with specified Zener voltage measured at 20 mA test current and thermal equilibrium at 30°C lead temperature. Its 5% tolerance and 23 Ω impedance support stable reference generation under moderate load variation.

The 1N748A_T50R adheres to absolute maximum ratings including 500 mW power dissipation at TL ≤ 75°C and -65°C to +200°C operating/storage temperature range. Forward voltage is 1.5 V max at 200 mA, confirming standard silicon PN junction behavior.

Key Specifications

Parameter	Value and Actual Design Meaning
V_Z @ I_Z = 20 mA	3.9 V nominal, ±5% tolerance - defines regulated output voltage accuracy in shunt regulator designs
Z_Z @ I_Z = 20 mA	23 Ω - determines output voltage stability under load current changes
I_ZM	95 mA - maximum safe continuous Zener current before thermal runaway at rated conditions
P_D @ T_L ≤ 75°C	500 mW - sets upper limit for power handling in lead-mounted configurations
Derating	4.0 mW/°C above 75°C - required linear reduction in power capability with rising lead temperature
Operating Temp	-65°C to +200°C - supports operation in extended industrial and automotive under-hood environments

Pinout & Package

DO-35 glass axial package with cathode indicated by color band; two-terminal device with anode and cathode leads.

Pin/Terminal	Circuit Role	Design Meaning
Anode	Forward conduction terminal / Zener reference ground node	Connected to circuit ground or lower potential in shunt regulation; carries forward current up to 200 mA
Cathode	Zener breakdown terminal / regulated output node	Connected to supply rail being regulated; maintains ~3.9 V relative to anode when reverse biased above knee voltage

Key Features

Feature	Design Value
±5% Zener voltage tolerance	Enables predictable regulation without post-manufacture trimming in cost-sensitive analog references
DO-35 glass package	Provides hermetic sealing and stable long-term parameter drift for reliability-critical applications
500 mW power rating	Supports direct shunt regulation of low-current rails (e.g., sensor bias, op-amp reference) without heatsinking
Low 23 Ω dynamic impedance	Minimizes output voltage deviation across 1–50 mA load current variations in feedback-free designs

Applications

Industrial Sensor Signal Conditioning	Microcontroller Voltage Reference
Use Scenario: Stabilizing excitation voltage for resistive bridge sensors in PLC analog input modules. IC Role / Device Role / Timing Role: Shunt voltage reference providing fixed 3.9 V bias to strain gauge bridges. Use Value: Maintains measurement linearity by holding bridge voltage within ±5% despite 12–24 V supply variation.	Use Scenario: Supplying precise reference to ADC internal voltage reference input in 8-bit microcontrollers. IC Role / Device Role / Timing Role: External Zener reference replacing less accurate internal bandgap sources. Use Value: Improves 10-bit ADC effective resolution by reducing reference drift to <10 mV over temperature.
Power Supply Overvoltage Clamp	Low-Power Analog Front-End Protection
Use Scenario: Clamping transient spikes on 5 V logic rails caused by relay switching or ESD events. IC Role / Device Role / Timing Role: Fast-acting crowbar element limiting rail voltage to 3.9 V + V_f during overvoltage. Use Value: Prevents latch-up in downstream logic ICs by clamping transients within 100 ns response time.	Use Scenario: Protecting op-amp inputs in battery-powered medical instrumentation front-ends. IC Role / Device Role / Timing Role: Input-stage voltage limiter preventing damage from accidental 9 V battery reversal or probe contact. Use Value: Limits input common-mode range to safe levels while drawing <1 µA leakage below 1 V reverse bias.

Industrial Sensor Signal Conditioning

Microcontroller Voltage Reference

Use Scenario: Stabilizing excitation voltage for resistive bridge sensors in PLC analog input modules.

IC Role / Device Role / Timing Role: Shunt voltage reference providing fixed 3.9 V bias to strain gauge bridges.

Use Value: Maintains measurement linearity by holding bridge voltage within ±5% despite 12–24 V supply variation.

Use Scenario: Supplying precise reference to ADC internal voltage reference input in 8-bit microcontrollers.

IC Role / Device Role / Timing Role: External Zener reference replacing less accurate internal bandgap sources.

Use Value: Improves 10-bit ADC effective resolution by reducing reference drift to <10 mV over temperature.

Power Supply Overvoltage Clamp

Low-Power Analog Front-End Protection

Use Scenario: Clamping transient spikes on 5 V logic rails caused by relay switching or ESD events.

IC Role / Device Role / Timing Role: Fast-acting crowbar element limiting rail voltage to 3.9 V + V_f during overvoltage.

Use Value: Prevents latch-up in downstream logic ICs by clamping transients within 100 ns response time.

Use Scenario: Protecting op-amp inputs in battery-powered medical instrumentation front-ends.

IC Role / Device Role / Timing Role: Input-stage voltage limiter preventing damage from accidental 9 V battery reversal or probe contact.

Use Value: Limits input common-mode range to safe levels while drawing <1 µA leakage below 1 V reverse bias.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
1N4728A	3.3 V nominal Zener voltage, same DO-35 package and 5% tolerance	Lower regulation voltage limits use in 3.3 V systems; higher 100 mA I_ZM allows greater surge handling	Select when 3.3 V reference is required and higher current margin is needed
BZX55-C3V9	Same 3.9 V nominal, ±5% tolerance, but rated 500 mW at T_A = 25°C (not lead-temperature based)	Thermal performance differs: BZX55-C3V9 uses ambient-rated derating vs. 1N748A_T50R's lead-temperature method	Choose when board-level ambient temperature control is preferred over lead-mount thermal management

Compared with 1N748A_T50R, 1N4728A offers lower voltage and higher current headroom, while BZX55-C3V9 shifts thermal rating methodology from lead-temperature to ambient-based derating-impacting layout-dependent thermal design decisions.

Availability

1N748A_T50R is available at Aetrix Electronics and suitable for industrial sensor signal conditioning, microcontroller voltage reference, and power supply overvoltage clamp applications requiring stable component supply and long-lifecycle availability.

Supply support for 1N748A_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 1N748A_T50R belongs to Fairchild's legacy 1N7xxA series of general-purpose Zener diodes, designed for cost-effective voltage regulation and protection in industrial, consumer, and computing power supplies.

FAQ

What is the nominal Zener voltage and tolerance of the 1N748A_T50R?

The 1N748A_T50R has a nominal Zener voltage of 3.9 V with a tolerance of ±5%, measured at 20 mA test current and thermal equilibrium at 30°C lead temperature. This specification ensures predictable regulation performance in shunt reference and clamp applications where voltage accuracy directly impacts system functionality.

How does the 1N748A_T50R handle thermal derating above 75°C?

The 1N748A_T50R derates linearly at 4.0 mW/°C above a lead temperature of 75°C, meaning its maximum allowable power dissipation decreases proportionally as lead temperature rises. This behavior requires careful PCB layout with adequate copper pour and lead length control to maintain reliability in high-temperature environments.

What is the maximum Zener current rating for the 1N748A_T50R?

The 1N748A_T50R has a maximum Zener current (I_ZM) of 95 mA at 25°C ambient, determined by its 500 mW power rating and 3.9 V Zener voltage. This value decreases with increasing temperature due to thermal derating, and must be verified against actual operating conditions using the published derating curve.

Is the 1N748A_T50R suitable for use as a voltage reference in precision ADC circuits?

Yes, the 1N748A_T50R can serve as a basic voltage reference in precision ADC circuits where ±5% accuracy and moderate temperature drift are acceptable. Its 23 Ω dynamic impedance helps stabilize the reference node, though for higher accuracy, dedicated reference ICs with lower drift and tighter tolerance are recommended alongside the 1N748A_T50R.

What package type and marking convention does the 1N748A_T50R use?

The 1N748A_T50R uses a DO-35 glass axial package with cathode identified by a color band. Marking consists of three lines: Fairchild logo (F), "48" (4th–5th characters of part number), and "A" (6th–7th characters), conforming to Fairchild's standard top-marking specification for 1Nxx series devices.

1N748A_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):: 3.9 V

Tolerance:: ±5%

Power - Max:: 500 mW

Impedance (Max) (Zzt):: 23 Ohms

Current - Reverse Leakage @ Vr:: 10 µA @ 1 V

Voltage - Forward (Vf) (Max) @ If:: 1.5 V @ 200 mA

Operating Temperature:: -65°C ~ 200°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: DO-35

1N748A_T50R FAQ

1.How can I place an order for 1N748A_T50R through Aetrix?

Please submit a Request for Quotation (RFQ) for 1N748A_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 1N748A_T50R reliable?

The price and inventory of 1N748A_T50R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N748A_T50R is usually 5 days.

3.What payment methods are accepted for 1N748A_T50R?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N748A_T50R transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 1N748A_T50R?

1N748A_T50R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 1N748A_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 1N748A_T50R?

For technical support, including 1N748A_T50R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N748A_T50R requirements.

6.How does Aetrix verify that 1N748A_T50R is sourced from the original manufacturer or authorized distributors?

All 1N748A_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 1N748A_T50R meets industry standards.

7.What is the process for return or replacement of 1N748A_T50R?

All 1N748A_T50R units undergo pre-shipment inspection (PSI). If there is an issue with 1N748A_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 1N748A_T50R part is unused and in its original packaging.

Return procedure for 1N748A_T50R:

1.Submit a request within 90 days.

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

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