How to find the right Gas Tube Arrestors AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Gas Tube Arrestors
- DC sparkover voltage
- Choose a DC sparkover voltage comfortably above the line's peak working voltage, allowing for the part's tolerance, which is commonly ±20%. If sparkover is too low, the tube fires on normal signals or ringing voltage. If it is too high, it lets damaging energy through.
- Impulse sparkover
- Check the impulse sparkover at the expected rate of rise, for example 100 V/µs or 1 kV/µs. It is much higher than the DC sparkover. A GDT conducts later and at a higher voltage on fast surges, so downstream parts must survive that let-through.
- Surge current capacity
- Size the nominal discharge current on the 8/20 µs waveform for the exposure. Outdoor and antenna lines need the higher kA classes. Repeated surges near the limit shift the sparkover voltage and shorten the tube's life.
- Follow-on current on powered lines
- Do not place a GDT alone across a DC or AC supply that can sustain current above its arc voltage. Put a MOV or resistor in series, or use a part specified for power-line use. Once fired, the arc can latch on and short the supply until the tube fails.
- Electrode count
- Use 3-electrode tubes for balanced pairs such as telecom tip and ring, and 2-electrode tubes for single lines. A 3-electrode tube fires both lines to ground together, which avoids converting a common-mode surge into a differential one.
- Fail-safe option
- For unattended telecom or outdoor equipment, prefer versions with a fail-short (thermal) mechanism. A tube that fails open leaves the line unprotected without any visible sign.
Brands that matter
- Bourns: Wide GDT range, including 2- and 3-electrode telecom parts.
- Littelfuse: GDTs in leaded and SMD packages with detailed datasheets.
- TDK (EPCOS): Long-established GDT maker for telecom and industrial use.
- Eaton Bussmann: GDTs within a broader circuit protection lineup.
What to avoid
- Unmarked glass or ceramic tubes with no published sparkover tolerance.
- Using a GDT as the only protection for fast-edge, low-voltage ICs without a TVS stage behind it.
- Placing a GDT directly across mains or battery rails without follow-on current control.
Questions
Why does my GDT need a TVS or MOV with it?
A GDT handles large energy but fires late and at a high voltage. Pairing it with a faster clamp downstream, separated by a resistor or inductor, protects sensitive parts during the first nanoseconds.