What is  Guard-ring?

A Guard ring is used to prevent the latch-up effect in Analog Layout design. in another way, we can say that a guard ring is used to prevent the minority charge carrier injection in the substrate or well.

In analog layout design, guard rings are used to entirely enclose a collection of devices. Guard rings more effectively isolate them from one another. This stops other devices’ potential fluctuations or charges accumulation from affecting the performance of the inside circuit. Generally, Guard rings are used in analog devices. 

Types of Guard-ring?

There are two types of guard rings,

N+ Guard Ring

N+ Guard Ring is designed into NWELL, which will collect holes as a minority charge carrier into NWELL, and it will help to prevent the latch-up.

P+ Guard Ring

P+ Guard Ring is designed into P- Substrate, which will collect electrons as a minority charge carrier into P- Substrate, and it will help to prevent the latch-up.

P+ Guard-ring

Use of the Gaurd- ring

• In Analog Devices,
• Latch-up prevention
• For device isolation purposes,
• Create strong ohmic contact with the substrate or well