Current detection circuit
AssigneeRohm Co., Ltd.
InventorsYoichi Tamegai, Satoru Nate, Isao Yamamoto
Life of this patent
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Abstract
A first transistor may be provided on a current path of a photo transistor. The bias current path may include a bias switch and a first bias resistor connected in series and is provided in parallel with a main current path including the phototransistor. A second transistor may configure a current mirror circuit with the first transistor, and generates second current formed by multiplying the first current flowing in the first transistor by a predetermined factor. The second current is charged in the charging capacitor and converted into a voltage. The bias current path turns on prior to the start of light reception of the phototransistor and turns off after a predetermined period has elapsed from the start of light reception of the phototransistor.
Claims23
A current detection circuit for detecting current flowing in a light receiving device connected to a detection terminal, the current detection circuit comprising:
- a first transistor, one end thereof connected to a first end of a main current path including the light receiving device and the detection terminal, a potential of a second end of the main current path being fixed;
- a bias current path which is on-off controllable, a first end thereof connected to the first end of the main current path, a second end thereof connected to the second end of the main current path;
- and
- a second transistor which configures a current mirror circuit with the first transistor and forms output of the current detection circuit by multiplying the current flowing in the first transistor by a predetermined factor, wherein
- the bias current path is configured to turn on prior to the start of light reception of the light receiving device, and
- a sum of the current through the main current path and the current through the bias current path flows into the first transistor.
A current detection circuit for detecting current flowing in a light receiving device, comprising:
- a first transistor which is provided on a current path of the light receiving device in series with the light receiving device;
- a charging capacitor with a potential at one end fixed;
- a second transistor which configures a current mirror circuit with the first transistor, multiplies the current flowing in the first transistor by a predetermined factor, and charges the charging capacitor;
- and
- a discharge switch which is provided in parallel with the charging capacitor,
- wherein
- the discharge switch is configured to turn on for a predetermined period prior to the start of light reception of the light receiving device, and
- a current flowing in the light receiving device flows into an emitter, a source, a collector, or a drain of the first transistor.
Dependencies are inferred from the claim text.