TVS diode symbol | Uni-directional Bidirectional TVS diode

Transient Voltage Suppression diode is a type of semiconductor device. TVS diode is designed to protect electronic components and circuits from voltage spikes and transients. They are solid state pn junction devices. The figure-1 mentions TVS diode symbol.

TVS diode symbols

Surge power as well as surge current of TVS diode depend on junction area. Larger the cross section area of the TVS diode, higher is the absorbing capacity to absorb transient currents.

The major difference between TVS diode and zener diode is that TVS diodes are designed to suppress transient voltage while zener diodes are designed to regulate voltage.

There are two main types of TVS diodes viz. uni-directional and bidirectional. Uni-directional TVS diodes are designed to protect against voltage spikes in one direction only while Bidirectional TVS diodes can handle voltage spikes in both directions. Hence bidirectional TVS diodes are used where the polarity of the voltage surge may vary.

Let us understand, working principle of TVS diode with the help of its one application in the following schematic circuit diagram example.

TVS diode working principle

TVS diodes work by rapidly clamping the voltage across them when it exceeds a certain predefined threshold. They have a very fast response time and can divert the excess voltage away from the circuit to be protected . Hence it prevents damage of the components. This clamping action of TVS diode is achieved through a combination of its intrinsic properties and design.

In normal operating conditions, TVS diode will introduce high impedance to protected circuit. In the condition when normal voltage exceeds, TVS diode junction avalanches and inserts low impedance path for the transient current.

TVS diode application

Due to this transient current is deviated away. Hence circuit is protected. Voltage across the circuit is limited to TVS diode clamping voltage. After the transient threat vanishes, diode device returns to high impedance state.

The major benefits of using TVS diode is that the device does not wear out. Moreover there will not be any degradation in its electrical parameters. TVS diodes in wide range of voltages are available. Typically the diodes are available from 5 Volt to 440 Volt.

They are used as board level protectors for semiconductors as well other sensitive parts. The applications of TVS diode include MOS memory, AC power lines, signal and data lines, telecommunication equipments etc.

Recently Littelfuse Inc. has launched 6 new series of highly reliable TVS diodes. These diodes are used for aerospace applications.

As mentioned TVS diodes are mainly used for protection applications. These diodes will protect sensitive electronic equipments from lightning surges as well as unwanted voltage transients.

TVS diode Manufacturers/Vendors

Following are popular TVS diode manufacturers/vendors:
• Semtech Corporation
• Digikey
• ON semiconductor
• Vishay
• Littelfuse Inc.
• Bourns

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