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onsemi 1N749A_T50A
- Part No.:
- 1N749A_T50A
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-204AH, DO-35, Axial
- Datasheet:
-
1N749A_T50A.pdf
- Description:
- DIODE ZENER 4.3V 500MW DO35
- Quantity:
- Payment:
- Shipping:
Inventory:4,243
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Product details
Overview
1N749A_T50A from Fairchild Semiconductor is a 5.1 V, ±5% tolerance silicon Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C, with 22 Ω dynamic impedance at 20 mA and 85 mA maximum zener current, used for precision voltage regulation and reference in low-power analog circuits.
For engineers reviewing the 1N749A_T50A datasheet, pinout, applications, or equivalent options, key selection criteria include zener voltage tolerance, thermal derating behavior, leakage current at 1 V reverse bias (2 µA), and compatibility with through-hole PCB layouts requiring axial leaded DO-35 devices.
Technical Context
This Zener diode operates in reverse breakdown mode to maintain stable voltage across its terminals under varying load conditions. Its 5.1 V nominal zener voltage is specified at 20 mA test current, with 22 Ω dynamic impedance indicating moderate regulation sensitivity to current changes.
The device follows standard 1N-series marking: cathode band denotes polarity, top mark "F/49/A" confirms identity as 1N749A, and it complies with absolute maximum ratings including -65°C to +200°C operating/storage temperature range and 4.0 mW/°C thermal derating above 75°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VZ @ IZ = 20mA | 4.09 V (min) to 4.52 V (max); defines usable regulation window under standard test condition |
| Tolerance | ±5%; determines worst-case output voltage deviation in reference designs |
| ZZ @ IZ = 20mA | 22 Ω; quantifies voltage change per mA shift in zener current |
| IZM | 85 mA; maximum safe continuous reverse current before thermal runaway risk |
| IR @ VR = 1V | 2 µA; reverse leakage level affecting high-impedance bias networks |
| PD @ TL ≤ 75°C | 500 mW; sets upper power limit for stable operation without heatsinking |
| Package | DO-35 glass; axial-leaded, hermetically sealed, industry-standard through-hole footprint |
Pinout & Package
DO-35 glass package: axial leads, cathode identified by color band; no active pinout beyond anode/cathode polarity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower-potential node in reverse-biased regulation configuration |
| Cathode | Zener breakdown terminal | Marked with color band; connected to regulated output node in shunt regulator topology |
Key Features
| Feature | Design Value |
|---|---|
| Stable 5.1 V reference | Guaranteed 4.09–4.52 V range at 20 mA enables predictable analog circuit biasing |
| Low leakage current | 2 µA max at 1 V reverse bias minimizes error in high-resistance divider networks |
| Hermetic DO-35 package | Glass encapsulation ensures long-term stability and moisture resistance in industrial environments |
| Wide temperature range | -65°C to +200°C operation supports automotive under-hood and aerospace applications |
Applications
| Power Supply Reference | Overvoltage Clamp |
|---|---|
Use Scenario: Providing stable 5.1 V reference for linear regulators or ADC voltage references in battery-powered instrumentation. IC Role / Device Role / Timing Role: Shunt voltage reference diode maintaining fixed potential across feedback network. Use Value: ±5% tolerance and 22 Ω impedance ensure <10 mV output variation over 5–25 mA load range. | Use Scenario: Protecting microcontroller I/O pins from transient voltage spikes on sensor interface lines. IC Role / Device Role / Timing Role: Reverse-biased clamping element diverting excess energy to ground when voltage exceeds 4.52 V. Use Value: 2 µA leakage at 1 V prevents signal distortion in high-impedance analog inputs. |
| Current Source Bias | Temperature-Stable Oscillator Trim |
Use Scenario: Setting bias current for op-amp input stages using constant-voltage drop across series resistor. IC Role / Device Role / Timing Role: Precision voltage source defining current magnitude via Ohm's law. Use Value: 500 mW power rating allows up to 98 mA bias current with 5.1 V drop before thermal derating applies. | Use Scenario: Compensating oscillator frequency drift in crystal-based real-time clocks via voltage-controlled trim network. IC Role / Device Role / Timing Role: Stable DC reference adjusting varactor diode capacitance in tuning loop. Use Value: -65°C to +200°C operating range ensures consistent trim voltage across extended environmental profiles. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4733A | Same 5.1 V nominal, but ±5% tolerance, 500 mW rating, and DO-41 package (larger than DO-35) | Requires PCB pad redesign due to longer body and wider lead spacing | Preferred where higher surge current capability or legacy DO-41 footprint is required |
| BZX55-C5V1 | 5.1 V, ±5%, 500 mW, but in DO-35 package with 100 nA IR @ 1 V (lower leakage) | Superior for ultra-low-power bias networks where sub-µA leakage matters | Chosen when minimizing reverse leakage dominates over legacy 1N-series marking compatibility |
Compared with 1N749A_T50A, 1N4733A offers identical regulation but requires layout adaptation, while BZX55-C5V1 delivers lower leakage in same DO-35 form factor-making it suitable for precision low-current references where 1N749A_T50A's 2 µA IR may introduce measurable error.
Availability
1N749A_T50A is available at Aetrix Electronics and suitable for voltage reference, overvoltage protection, and analog biasing applications requiring stable component supply across industrial control, test equipment, and embedded sensor subsystems.
Supply support for 1N749A_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 components before its acquisition by ON Semiconductor in 2016.
The 1N749A_T50A belongs to Fairchild's legacy 1N7xxA Zener diode family, designed for general-purpose voltage regulation and reference in cost-sensitive, low-to-medium power linear circuits.
FAQ
What is the nominal zener voltage of the 1N749A_T50A?
The 1N749A_T50A has a nominal zener voltage of 5.1 V, with a guaranteed range of 4.09 V (minimum) to 4.52 V (maximum) at 20 mA test current and 25°C ambient. This specification is defined in Fairchild's official datasheet Rev. D1 and reflects the device's ±5% tolerance grade. The 1N749A_T50A achieves this regulation in reverse breakdown mode and is intended for use in shunt-type voltage reference configurations.
What package type does the 1N749A_T50A use?
The 1N749A_T50A uses the DO-35 glass axial-leaded package, identified by a cathode color band and top marking "F/49/A". This hermetically sealed package supports operating temperatures from -65°C to +200°C and is compatible with standard through-hole assembly processes. The 1N749A_T50A's DO-35 footprint differs from larger packages like DO-41, requiring specific land patterns in PCB layout.
What is the maximum power dissipation rating for the 1N749A_T50A?
The 1N749A_T50A is rated for 500 mW power dissipation at lead temperature (TL) ≤ 75°C with 3/8″ lead length. Above 75°C, it must be derated at 4.0 mW/°C. This rating defines the upper thermal limit for continuous operation without forced cooling. The 1N749A_T50A's actual safe operating current depends on ambient conditions and board-level heat sinking, especially given its 22 Ω dynamic impedance and 85 mA IZM.
How does the 1N749A_T50A compare to the 1N4733A in terms of electrical performance?
The 1N749A_T50A and 1N4733A both provide 5.1 V zener regulation with ±5% tolerance and 500 mW power rating, but differ in package (DO-35 vs. DO-41) and dynamic impedance (22 Ω vs. 17 Ω). The 1N749A_T50A exhibits higher leakage (2 µA @ 1 V) than the 1N4733A (10 µA @ 1 V), making the 1N749A_T50A more suitable for low-leakage bias networks. Both are functionally interchangeable only with mechanical adaptation.
Is the 1N749A_T50A suitable for automotive under-hood applications?
Yes, the 1N749A_T50A supports operating temperatures from -65°C to +200°C and is housed in a hermetic DO-35 glass package, making it suitable for under-hood automotive applications where thermal cycling and humidity resistance are critical. Its 5.1 V regulation stability across temperature, combined with low leakage and robust construction, aligns with requirements for engine control sensor references and power rail clamping. The 1N749A_T50A meets these needs without requiring additional conformal coating.
1N749A_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):
- 4.3 V
- Tolerance:
- ±5%
- Power - Max:
- 500 mW
- Impedance (Max) (Zzt):
- 22 Ohms
- Current - Reverse Leakage @ Vr:
- 2 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
1N749A_T50A FAQ
1.How can I place an order for 1N749A_T50A through Aetrix?
Please submit a Request for Quotation (RFQ) for 1N749A_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 1N749A_T50A reliable?
The price and inventory of 1N749A_T50A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1N749A_T50A is usually 5 days.
3.What payment methods are accepted for 1N749A_T50A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1N749A_T50A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1N749A_T50A?
1N749A_T50A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1N749A_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 1N749A_T50A?
For technical support, including 1N749A_T50A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1N749A_T50A requirements.
6.How does Aetrix verify that 1N749A_T50A is sourced from the original manufacturer or authorized distributors?
All 1N749A_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 1N749A_T50A meets industry standards.
7.What is the process for return or replacement of 1N749A_T50A?
All 1N749A_T50A units undergo pre-shipment inspection (PSI). If there is an issue with 1N749A_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 1N749A_T50A part is unused and in its original packaging.
Return procedure for 1N749A_T50A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1N749A_T50A Tags
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