Browse Prior Art Database

Solid State Relay for Communication Applications

IP.com Disclosure Number: IPCOM000061988D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Johnson, M: AUTHOR

Abstract

When connecting a number of digital terminal devices to a customer newtwork, relays are often used to open the communication line and insert the communicating terminal. Because electromechanical relays include mechanical motion and mechanical/electrical contacts, reliability is sometimes a problem, depen upon the environment in which the relays must be made to operate. This paper teaches the use of a pair of complementary field effect transistors to replace the normally open and normally closed contacts of a communication relay.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Solid State Relay for Communication Applications

When connecting a number of digital terminal devices to a customer newtwork, relays are often used to open the communication line and insert the communicating terminal. Because electromechanical relays include mechanical motion and mechanical/electrical contacts, reliability is sometimes a problem, depen upon the environment in which the relays must be made to operate. This paper teaches the use of a pair of complementary field effect transistors to replace the normally open and normally closed contacts of a communication relay.

As shown in the figure, the common terminal 11 of the mechanical relay is replaced by the commonly connected drains of transistors 17 and 19. FET 17 is normally conducting without a voltage at its gate whereas FET 19 is normally not conducting without a voltage at its gate. In order to switch the state of the relay, a oscillating signal is applied to the isolation transformer driving transistor 21 which causes current to be induced in the secondary winding 23 of the isolation transformer. This current is rectified by diode 25 causing a voltage drop across resistor 27 to turn transistor 17 off and turn transistor 19 on. Transistor 17 is of the depletion mode type and transistor 19 is of the complementary enhancement mode type.

Disclosed anonymously.

1