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onsemi BZX79C20
- Part No.:
- BZX79C20
- Manufacturer:
- onsemi
- Category:
- Single Zener Diodes
- Package:
- DO-204AH, DO-35, Axial
- Datasheet:
-
BZX79C20.pdf
- Description:
- DIODE ZENER 20V 500MW DO35
- Quantity:
- Payment:
- Shipping:
Inventory:143,000
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Product details
Overview
BZX79C20 from ON Semiconductor is a 20 V ±5% tolerance Zener diode in DO-35 glass package, rated for 500 mW power dissipation at TL ≤ 75°C, with 55 Ω dynamic impedance at 5 mA test current and 0.05 μA leakage current at 15.4 V reverse voltage. It serves as a precision voltage reference or overvoltage clamp in low-power analog and power supply feedback circuits.
For engineers reviewing the BZX79C20 datasheet, pinout, applications, or equivalent options, key selection criteria include its 20 V nominal Zener voltage, ±5% tolerance, 55 Ω Zener impedance, -2.0 mV/°C temperature coefficient, and DO-35 through-hole package compatibility with legacy board layouts.
Technical Context
The BZX79C20 operates as a silicon planar Zener diode optimized for stable voltage regulation in low-current applications. Its 20 V nominal breakdown voltage is specified at 5 mA test current (IZ), with a tight ±5% tolerance and a negative temperature coefficient of -2.0 mV/°C - indicating predictable downward drift with rising junction temperature.
It exhibits 55 Ω dynamic impedance (ZZ) at IZ = 5 mA, enabling consistent regulation under small-signal load variations, and maintains <0.05 μA leakage current up to 15.4 V (VR), supporting reliable blocking in standby or low-power modes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Zener Voltage (VZ) | 18.8 V min / 21.2 V max at IZ = 5 mA - defines usable regulation window for feedback or reference use |
| Tolerance | ±5% - ensures predictable voltage accuracy without individual calibration |
| Power Dissipation (PD) | 500 mW @ TL ≤ 75°C - supports continuous operation in compact PCB layouts with minimal heatsinking |
| Zener Impedance (ZZ) | 55 Ω max at IZ = 5 mA - limits output voltage variation under small load changes |
| Leakage Current (IR) | ≤0.05 μA at VR = 15.4 V - guarantees high off-state resistance in clamping or sensing roles |
| Temperature Coefficient (TC) | -2.0 mV/°C - enables predictable thermal drift compensation in stable reference designs |
| Package | DO-35 glass axial - compatible with wave-soldering and legacy through-hole assembly processes |
Pinout & Package
DO-35 glass axial package with cathode indicated by a color band on the body; two-terminal device with no internal connections beyond anode and cathode leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal | Connected to lower potential side in reverse-biased Zener configuration |
| Cathode | Zener breakdown terminal | Marked with color band; connected to higher potential side for regulation/clamping |
Key Features
| Feature | Design Value |
|---|---|
| ±5% Zener voltage tolerance | Enables direct replacement in cost-sensitive designs without trimming or calibration |
| 55 Ω dynamic impedance at 5 mA | Minimizes output voltage deviation across typical bias current fluctuations |
| -2.0 mV/°C temperature coefficient | Supports stable performance in ambient temperature ranges up to +125°C |
| 0.05 μA max leakage at 15.4 V | Ensures negligible standby current draw in battery-powered or energy-harvesting systems |
Applications
| Power Supply Feedback | Overvoltage Protection |
|---|---|
Use Scenario: Regulating output voltage in discrete linear regulators or SMPS feedback loops using TL431 alternatives. IC Role / Device Role / Timing Role: Zener reference element providing stable 20 V threshold for error amplifier input. Use Value: Tight ±5% tolerance and low 55 Ω impedance ensure accurate setpoint maintenance despite line/load transients. | Use Scenario: Clamping transient surges on 18–24 V rail inputs in automotive body electronics. IC Role / Device Role / Timing Role: Reverse-biased shunt protector diverting excess energy to ground above 21.2 V. Use Value: Low leakage (<0.05 μA) prevents false triggering; DO-35 package withstands reflow and mechanical stress. |
| Voltage Reference | Signal Level Shifting |
Use Scenario: Generating stable 20 V reference for ADC biasing or sensor excitation in industrial instrumentation. IC Role / Device Role / Timing Role: Precision DC reference source with predictable thermal drift (-2.0 mV/°C). Use Value: Enables ratiometric measurement stability without external temperature compensation circuitry. | Use Scenario: Biasing op-amp inputs or level-shifting logic signals between 3.3 V and 20 V domains. IC Role / Device Role / Timing Role: Clamp diode establishing fixed offset voltage in analog interface stages. Use Value: Low dynamic impedance ensures minimal signal distortion during fast edge transitions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Zener diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 1N4744A | 20 V nominal, ±5%, 1 W rating, DO-41 package, 22 Ω ZZ @ 5 mA | Higher power handling but larger footprint; not DO-35 drop-in | Choose when >500 mW dissipation or lower impedance is required |
| MMSZ5248B | 20 V nominal, ±5%, 500 mW, SOD-123 surface-mount package, 50 Ω ZZ @ 20 mA | Same power rating but SMT-only; different test current and thermal profile | Choose for space-constrained PCBs where through-hole is not feasible |
Compared with BZX79C20, the 1N4744A offers higher power and lower impedance but requires board redesign for DO-41; the MMSZ5248B matches power and voltage but demands SMT assembly and uses 20 mA test current - making BZX79C20 optimal for legacy DO-35 designs needing proven thermal stability and axial lead compatibility.
Availability
BZX79C20 is available at Aetrix Electronics and suitable for power supply feedback, overvoltage protection, and voltage reference applications requiring stable component supply, long-term obsolescence resilience, and DO-35 through-hole compatibility.
Supply support for BZX79C20 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
ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
The BZX79C series belongs to ON Semiconductor's general-purpose Zener diode product line, designed specifically for cost-effective, reliable voltage regulation and clamping in low-to-medium power analog and power management circuits.
FAQ
What is the nominal Zener voltage of the BZX79C20?
The BZX79C20 has a nominal Zener voltage of 20 V, with a guaranteed range of 18.8 V to 21.2 V at a test current of 5 mA and ambient temperature of 25°C. This value is defined per ON Semiconductor's datasheet Rev. 3 (November 2017) and reflects the device's ±5% tolerance specification. The BZX79C20 achieves stable regulation within this window under standard operating conditions.
What is the maximum power dissipation rating for the BZX79C20?
The BZX79C20 is rated for 500 mW power dissipation at a lead temperature (TL) of ≤75°C with 3/8" lead length. Above 75°C, it derates linearly at 4.0 mW/°C. This rating determines safe continuous operation in through-hole PCB layouts without forced cooling. The BZX79C20 must be mounted with appropriate lead length and thermal relief to maintain reliability within this limit.
Does the BZX79C20 have a specified temperature coefficient?
Yes, the BZX79C20 has a temperature coefficient of -2.0 mV/°C, meaning its Zener voltage decreases by approximately 2.0 mV for each degree Celsius rise in junction temperature. This value is measured and specified in the official ON Semiconductor datasheet. Designers using the BZX79C20 in temperature-varying environments should account for this drift, especially in precision reference applications.
What is the Zener impedance of the BZX79C20 and why does it matter?
The BZX79C20 exhibits a maximum dynamic impedance (ZZ) of 55 Ω at IZ = 5 mA. This parameter quantifies how much the Zener voltage changes with small variations in current - lower impedance means better regulation stability. In practice, this allows the BZX79C20 to maintain tighter voltage control in feedback networks or reference circuits where load or bias current may fluctuate slightly.
Is the BZX79C20 available in surface-mount packaging?
No, the BZX79C20 is exclusively offered in the DO-35 glass axial through-hole package, as confirmed by ON Semiconductor's official documentation. For surface-mount equivalents with similar electrical characteristics, consider the MMSZ5248B (SOD-123) or NZ9F20ST5G (SOD-923), though these differ in test current, thermal behavior, and mounting requirements. The BZX79C20 itself is not manufactured in SMT variants.
BZX79C20 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- DO-204AH, DO-35, Axial
- Packaging:
- Bulk
- Product Status:
- Active
- Voltage - Zener (Nom) (Vz):
- 20 V
- Tolerance:
- ±5%
- Power - Max:
- 500 mW
- Impedance (Max) (Zzt):
- 55 Ohms
- Current - Reverse Leakage @ Vr:
- 50 nA @ 14 V
- Voltage - Forward (Vf) (Max) @ If:
- 1.5 V @ 100 mA
- Operating Temperature:
- -65°C ~ 200°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- DO-35
BZX79C20 FAQ
1.How can I place an order for BZX79C20 through Aetrix?
Please submit a Request for Quotation (RFQ) for BZX79C20 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 BZX79C20 reliable?
The price and inventory of BZX79C20 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BZX79C20 is usually 5 days.
3.What payment methods are accepted for BZX79C20?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BZX79C20 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BZX79C20?
BZX79C20 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BZX79C20 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 BZX79C20?
For technical support, including BZX79C20 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BZX79C20 requirements.
6.How does Aetrix verify that BZX79C20 is sourced from the original manufacturer or authorized distributors?
All BZX79C20 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 BZX79C20 meets industry standards.
7.What is the process for return or replacement of BZX79C20?
All BZX79C20 units undergo pre-shipment inspection (PSI). If there is an issue with BZX79C20, 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 BZX79C20 part is unused and in its original packaging.
Return procedure for BZX79C20:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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