There are two types of Optical-coupled MOSFETs (OCMOS FET: Solid State Relay: SSR): "make" type ("a" contact: Normally open) and "break" type ("b" contact: Normally closed). The differences between these two types by operation is explained below.

If your browser supports JavaScript, you can manipulate them by clicking the "ON/OFF" or "STOP/GO" buttons.

1. "Make" Type ("a" Contact: Normally Open)

Th "make" type contains a couple of enhancement-type MOSFETs. They shut off by application of no bias, and conduct by application of forward bias.

The initial state is "OFF".

ON

1.

OFF

1.

2. "Break" Type ("b" Contact: Normally Closed)

The "break" type contains a couple of depletion-type MOSFETs. They conduct by application of no bias, and shut off by application of reverse bias.

The initial state is "GO".

STOP

2.

GO

2.