TVS tubes (Transient Voltage Suppression diodes) and varistors (Varistors) are common voltage protection components used to protect circuits from transient overvoltages. They have similar functions in circuit protection, but there are some differences in selection, performance characteristics, application scenarios and so on.

The following is a comparison of TVS tube and varistor selection:
1. How it works
    TVS tube (Transient Voltage suppression diode) : TVS tube suppresses voltage surge by rapid response. When a transient overvoltage is encountered, the TVS tube will be switched on in a very short time, diverting the excessive voltage to the ground, thereby protecting the sensitive components in the circuit. The main advantage of TVS tube is that the response speed is extremely fast, which is suitable for short and large voltage shocks.
    Varistor (Varistor) : A varistor is a component that works on the principle that the resistance value varies with voltage. Under normal operating voltage, the resistance of the varistor is very large, but when the voltage exceeds its breakdown voltage, the resistance will drop sharply, thereby diverting excessive current and inhibiting the influence of overvoltage on the circuit.

2. Response time
    TVS tube: Response time is very short, usually in the nanosecond level (ns), suitable for transient overvoltage (such as lightning strikes, switch surges, etc.) protection. Because of its extremely fast response speed, TVS tubes can be switched on even before the voltage rises.
Varistor: Response time is slow, usually in the microsecond level (? s). Although the response speed of the varistor can also cope with most surges, the response time is longer than that of the TVS tube.

3. Power handling capability

    TVS tube: TVS tube power processing capacity is generally high, can quickly consume large surge current. Generally used to suppress high-frequency, short-term transient voltage fluctuations.
     Varistor: varistor power processing capacity is relatively low, usually used for low power surge current suppression, but its surge resistance is strong, suitable for dealing with long-term voltage fluctuations and moderate intensity surge.

4. Stability and longevity
    TVS tube: The life of TVS tube is relatively short, especially in the high-intensity surge overvoltage environment, its protection function will gradually decay. Frequent surge events may cause the performance of TVS tubes to decline and eventually fail.
     Varistor: The stability of varistor is good, but under the impact of multiple surges, the resistance will gradually decrease, resulting in failure. Its life is usually longer than TVS tubes, but also depends on the frequency and intensity of surge events.

5. Voltage protection range
    TVS tube: TVS tube has different clamp voltage and breakdown voltage range, you can choose the appropriate voltage protection value according to demand. It is suitable for use where precise voltage protection is required.
     Varistor: Varistor protection voltage range is relatively wide, usually has a certain voltage range and large tolerance. When selecting, it is necessary to ensure that its breakdown voltage and rated operating voltage are suitable for the circuit requirements.

6. Application Scenarios
    TVS tube: widely used in high-speed data communication, power electronics, automotive electronics, industrial equipment and other occasions with high requirements for transient overvoltage protection. Suitable for protecting circuits from lightning strikes, power fluctuations, switch surges, etc.
     Varistor: Usually used for low-frequency surge protection, such as appliances, consumer electronics, low-voltage circuits, AC power supplies and other equipment protection. It is especially suitable for the protection of equipment with slow voltage overshoot.

7. Choose the basis
    When choosing TVS tubes, you need to consider:
    Characteristics of transient voltage (such as shock waveform, duration, etc.)
     Protection voltage requirements (breakdown voltage and clamp voltage)
     When choosing a varistor, you need to consider:
    Voltage range to ensure no misoperation under normal operating voltage
    Power capacity and energy absorption capacity

Sum up
    TVS tubes are suitable for applications requiring fast response and voltage protection, especially in high-frequency, high-energy transient surge protection.
    Varistors are suitable for general surge voltage protection, especially in situations where transient response times are less stringent.
    According to the specific application requirements, suitable voltage protection components can be selected to ensure the safe operation of the circuit.