公开(公告)号：JPH07193437A

公开(公告)日：1995-07-28

申请号：JP33300493

申请日：1993-12-27

Applicant: HITACHI LTD ,  HAMAMATSU PHOTONICS KK

Inventor： HASEGAWA ATSUSHI ,  YAMASHITA KIICHI ,  HASEGAWA YUTAKA ,  HAMAGISHI TAKAHIRO ,  KYOMASU MIKIO ,  SUZUKI TAKAYUKI

IPC: H03F3/08 ,  H03G3/30 ,  H04B10/07 ,  H04B10/2507 ,  H04B10/293 ,  H04B10/40 ,  H04B10/50 ,  H04B10/564 ,  H04B10/572 ,  H04B10/60 ,  H04B10/69 ,  H04L25/03 ,  H04B10/04 ,  H04B10/06 ,  H04B10/14 ,  H04B10/26 ,  H04B10/28

Abstract: PURPOSE:To output DC voltage at the time of a right input without light by operating as an amplifier when an incident light level is small and operating by lowering the gain and widening a light receiving dynamic range when the incidnet light level is large. CONSTITUTION:A differential amplfier 20 defines the output of a circuit by an inversion amplifier 3 and a gain switching circuit 22 as a positive input and defines the output of a reference voltage generation source circuit 24 by the inversion amplifier 10 and the gain switching circuit 23 having the same constitution as a negative input. Therefore, the amplifier 20 does not fluctuate DC voltage outputted at the time of an input without light before and after the switching of the gain of the inversion amplifiers 3 and 10. A gain switching control circuit 15 is composed of transistors 16 to 18, a current source 19 and a voltage source having set voltage V 1. When an input signal Vc 1 is higher than the set voltage V 1, the transistors 16 and 17 are turned off and current does not flow to the gain switching circuits 22 and 23 and diodes 7 and 15. As a result, a switching is performed so that the gain of the inversion amplifiers 3 and 10 may be increased.

公开(公告)号：JPH07131488A

公开(公告)日：1995-05-19

申请号：JP27073193

申请日：1993-10-28

Applicant: HAMAMATSU PHOTONICS KK ,  HITACHI LTD

Inventor： SUZUKI TAKAYUKI ,  KYOMASU MIKIO ,  YAMASHITA KIICHI ,  HASEGAWA ATSUSHI ,  HASEGAWA YUTAKA ,  HAMAGISHI TAKAHIRO

IPC: H04B10/40 ,  H04B10/50 ,  H04B10/524 ,  H04B10/60 ,  H04B10/80 ,  H04L25/02 ,  H04B10/04 ,  H04B10/06 ,  H04B10/14 ,  H04B10/26 ,  H04B10/28

Abstract: PURPOSE:To provide the driving circuit for light emitting elements which can drives a light emitting element at a high speed and facilitates light emission output control. CONSTITUTION:When a transistor(TR) QA1 turns off to stop supplying a current to the light emitting element D1, a TR QA3 connected to the light emitting element D1 in parallel turns on and the terminals of the light emitting element D1 is short-circuited. Therefore, when the light emitting element D1 lights out, electric charges accumulated in the parasitic capacitance of the light emitting element D1 are rapidly discharged. Further, when the TR QA1 turns on to start supplying the current to the light emitting element D1, a TR QA1 turns on at the same time and a current signal D having a peak at the time of its rise flows to the light emitting element D1. Therefore, when the light emitting element D1 illuminates, the capacitance C1 parasitic to the light emitting element D1 is speedily charged with the peak component at the time of the rise of the current signal D.