公开(公告)号：JPH09172411A

公开(公告)日：1997-06-30

申请号：JP27199796

申请日：1996-10-15

Applicant: IBM

Inventor： RABI SHIYANKAA ANASU ,  SAJIIRU MUNISUWAMI GOODA ,  MAAKU SAMUSON MIRUSHIYUTEIN ,  MAAKU BII RITSUTAA ,  DENISU RII ROJIYAAZU

IPC: H04B10/60 ,  H04B10/07 ,  H04B10/114 ,  H04B10/40 ,  H04B10/50 ,  H04B10/69 ,  H04B10/28 ,  H04B10/04 ,  H04B10/06 ,  H04B10/14 ,  H04B10/26

Abstract: PROBLEM TO BE SOLVED: To obtain an automatically adaptive threshold setting circuit by measuring a current flowing a reverse bias IR light detector corresponding to the surrounding light level and using this current for adjusting the sensitivity of a receiver. SOLUTION: The current flowing through a resistor 21 is a function of surrounding light in the light detector 11, the outputs of a buffer and a level shifter 22 becomes input to a current mirror consisting of transistors 23 and 24, and the current mirror operates as a variable impedance. One input of a level restoring circuit 26 is connected to the positive input of an amplifier 17 to be a node A and the other input is connected to a node B. A threshold is set by drawing a current through a resistor 25 and generating voltage at the node B so as to sense a voltage level at the output of the post amplifier 17. Then voltage at a node C is always offset from a level at the node A to be positive and this offset quantity is the threshold.