The answer to whether TVS diodes are polarized is: It depends on the type. TVS diodes come in two main variations, some of which are polarized and some are not.
Understanding TVS Diode Types
TVS (Transient Voltage Suppressor) diodes are specialized components designed to protect electronic circuits from voltage spikes, such as those caused by lightning strikes or inductive load switching. According to the reference, TVS diodes are categorized into two types:
- Unidirectional TVS Diodes: These are polarized.
- Bidirectional TVS Diodes: These have no polarity.
Unidirectional vs. Bidirectional
Let's look at the characteristics of each type regarding polarity.
Unidirectional TVS Diodes
These diodes are similar in behavior to standard rectifier diodes but are designed for clamping transient voltages. They conduct easily in one direction (forward bias) and block voltage up to their breakdown voltage in the other direction (reverse bias). Once the reverse voltage exceeds their breakdown voltage, they rapidly conduct to clamp the voltage.
As stated in the reference: "The positive and negative poles of the unidirectional TVS tube are marked, a white bar or a white circle is the negative pole, and the unmarked end is the positive pole." This marking clearly indicates their polarity, meaning they must be installed in a specific orientation within a circuit.
Bidirectional TVS Diodes
Unlike unidirectional types, bidirectional TVS diodes can clamp voltage spikes in both positive and negative directions relative to their ground reference. They behave like two unidirectional TVS diodes connected back-to-back in series.
Crucially, the reference states that "bidirectional TVS diodes have no polarity". This means they do not have a designated positive or negative end and can be installed in either orientation within the circuit without affecting their protective function.
Polarity and Marking Summary
Here’s a simple breakdown based on the reference:
| TVS Diode Type | Polarity | Marking (Unidirectional) |
|---|---|---|
| Unidirectional | Yes | White bar/circle = Negative, Unmarked end = Positive |
| Bidirectional | No | Typically unmarked for polarity |
In summary, if you are working with a unidirectional TVS diode, polarity is critical for correct operation and installation, and it will be clearly marked. If you are using a bidirectional TVS diode, polarity is not a concern.
