ISOLATION AMPLIFIER

• US 20190331527A1
• Filed: 10/20/2017
• Published: 10/31/2019
• Est. Priority Date: 12/06/2016
• Status: Abandoned Application

• Current Assignee: NTN Corporation
• Original Assignee: NTN Corporation
• Inventors: HANEDA, Masaji
• Application Number:
  US16/467,372
• Publication Number:
  US 20190331527A1
• Time in Patent Office: Days
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01J 2001/4413 Type
• CPC Class Codes: G01J 2001/4473 Phototransistor
• CPC Class Codes: H01L 31/12 structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto semiconductor devices with at least one potential barrier or surface barrier adapted for light emission H01L33/00; amplifiers using electroluminescent element and photocell H03F17/00; electroluminescent light sources per se H05B33/00
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 2200/276 the DC-isolation amplifier, e.g. chopper amplifier, modulation/demodulation amplifier, uses optical isolation means, e.g. optical couplers
• CPC Class Codes: H03F 3/085 using opto-couplers between stages
• CPC Class Codes: H03F 3/50 Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower

Abstract

A current Iin is separated into currents I1 and I2. When I1 flows in a light emitting diode D1, the diode D1 emits light and the current path of a phototransistor Q1 becomes conductive. At that time, current Iout flows in a light emitting diode D2. When the diode D2 emits light, the current path of a phototransistor Q2 becomes conductive, and I2 flows. If the value of the current Iout is large, the light emitting strength of the diode D2 is large. A large current I2 flows in the phototransistor Q2, which decreases the value of the current I1 flowing in the diode D1. As a result, the light emitting strength of the diode D1 becomes small, and the value of the current Iout decreases. In this manner, since a photocoupler P2 functions as a negative feedback circuit, linearity of the current Iin and the current Iout improves.

Claims

1. An isolation amplifier comprising:

a first and a second light coupling elements which include a light emitting element which emits light in accordance with a current flowing, and a light receiving element which carries a current in accordance with the light strength generated from the light emitting element;

the light emitting element included in the first light coupling element and the light receiving element included in the second light coupling element are connected in parallel;

the light receiving element included in the first light coupling element and the light emitting element included in the second light coupling element are connected in series; and

when a current is input into the circuit comprised of the light emitting element and the light receiving element connected in parallel, a current flowing in the circuit comprised of the light emitting element and the light receiving element connected in series, or a voltage in accordance therewith is output.