Varistors (Voltage Dependent Resistors - VDR) are passive electronic components that protect circuits from excessive transient voltages.

They exhibit a highly nonlinear current-voltage characteristic: high resistance at low voltage, rapidly decreasing resistance at high voltage.

Key Features:

• Clamps transient overvoltages (e.g., ESD, surges)
• Commonly made from zinc oxide (ZnO) or silicon carbide (SiC)
• Used in parallel with the load
• Fast response time (nanoseconds)
• Degrades slightly with each surge event

Typical Applications:

• Power supply protection
• Surge protectors
• Input/output line protection
• AC mains filtering

Note: Always check clamping voltage, energy rating, and response time for your application.