United States Patent  [ii] Patent Number: 4,742,309
Chu  Date of Patent: May 3,1988
 LINE RECEIVER
 Inventor: John W. Chu, Cupertino, Calif.
 Assignee: Dual-Lite Manufacturing Inc., Naguabo, P.R.
 Appl. No.: 948,313
 Filed: Dec. 31,1986
 Int. CI.* H03F 3/45
 U.S. CI 330/258; 330/257
 Field of Search 330/252, 257, 258, 288,
 References Cited
U.S. PATENT DOCUMENTS
Re. 29,700 7/1978 van de Plassche 330/257
4,634,993 1/1987 Koen 330/258 X
4.636.743 1/1987 Cotreau 330/257 X
4.636.744 1/1987 King et al 330/257 X
Primary Examiner—Eugene R. LaRoche
An improved line receiver with high common mode rejection is operable at voltages above the power supply voltage (VCC) as well as below ground. Input resistors provide high input impedence as well as means through which current summing of current mirror currents at the input transistor base nodes is translated into voltage drops which boosts the common mode rejection range of the circuit. Built-in hysteresis circuitry ensures proper detection of non-common mode signals. The high input impedence and high sensitivity allow multiple receivers of the type to be connected in parallel across a common bus for interrogation by a remote system. The preferred embodiment of the present invention is implemented in integrated circuit technology.
10 Claims, 5 Drawing Sheets