How to find the right Zener Diodes AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Zener Diodes
- Zener voltage and test current
- Vz is specified at a test current (Izt) on the datasheet; bias near that current to get the stated voltage At much lower currents the voltage sits noticeably below nominal, especially for low-voltage parts.
- Tolerance
- Read the suffix letter: in BZX55/BZX79 naming, 'C' means about 5% and 'B' about 2%; the 'A' suffix on 1N47xx and 1N52xx parts is the tighter grade Tolerance decides whether a part works as a loose clamp or a usable reference.
- Power rating
- Dissipation is Vz × Iz; keep it well below the rating after temperature derating. Common classes: 500 mW (1N52xx, BZX55, BZX79 in DO-35), 1W (1N47xx in DO-41), 5W (1N53xx) An undersized Zener overheats and drifts or fails short.
- Series resistor
- Always limit current with a series resistor sized for the worst-case supply voltage and minimum load Without a current limit, a Zener in breakdown conducts until it burns out.
- Temperature coefficient
- Parts around 5 to 6V have the lowest drift; below about 5V the knee is soft and regulation is poor For tight or low-voltage references, a shunt regulator such as the TL431 or a dedicated voltage reference performs better than a Zener.
Brands that matter
- Vishay: Broad Zener range in the BZX and 1N series, glass and SMD.
- onsemi: Classic 1N47xx, 1N52xx and 1N53xx families with detailed datasheets.
- Nexperia: BZX84 and similar SMD Zeners in SOT-23 and SOD packages.
- Diodes Incorporated: Wide SMD Zener selection.
- Rohm: Compact SMD Zeners for dense boards.
What to avoid
- Using a Zener as a high-current regulator when a linear or switching regulator fits better
- Choosing a sub-5V Zener when you need a precise reference
- Using a Zener for surge or ESD protection where a TVS diode is the right part
Questions
Which way round does a Zener go?
In regulation it is reverse biased: the banded cathode connects toward the positive supply through the series resistor, and the anode goes to ground.
Is a Zener the same as a TVS diode?
No. Both use reverse breakdown, but TVS diodes are built to absorb short, high-energy surges, while Zeners are meant for steady low-current clamping and references.