Couplers, also known as power distribution components, according to its different electronic devices in the display of different characteristics, the coupler can be divided into directional couplers, power dividers and a variety of microwave branch devices. For example, we may use optical fiber couplers in optical fiber transmission, where the primary role is to achieve optical signal splitting / routing, Coupler or to extend the fiber link components. And we usually use some of the power system and hydraulic coupler, the main role is to connect the power source and work machine, relying on changes in the momentum of the liquid torque transmission torque of the hydraulic device.
Coupler is a kind of electric-to-electrical conversion device that transmits electrical signals based on light. It consists of two parts: the light source and the receiver. The light source and the light receiver are assembled in the same closed case and are separated from each other by a transparent insulator. The source of the light source is the input terminal, the pin of the receiver is the output terminal. Coupler The common light source is the light emitting diode, the photodiode is the photodiode, the phototransistor and so on. Coupler types are more common common photodiode type, photoelectric transistor type, photoresistor type, light control thyristor type, photoelectric Darlington type, integrated circuit type.
The intensity of the light depends on the magnitude of the excitation current, Coupler which is irradiated to the receiver on the receiver, and the photocurrent is generated by the photoelectric effect. The light is supplied from the receiver output Leads, so that the realization of a light of a power conversion.
Basic operating characteristics (to photosensitive transistor as an example)
1, the common mode rejection ratio is very high
Coupler inside the coupler, because the coupling between the LED and the receiver is very small (2pF or less) so the common-mode input voltage through the inter-pole coupling capacitor on the output current is very small, Coupler so the common mode rejection ratio is high.
2, the output characteristics
The output characteristic of the coupler is the relationship between the bias voltage VCE and the output current IC applied by a certain light-emitting current IF. When IF = 0, the light-emitting diode does not emit light, and the phototransistor collector The output current is called a dark current and is generally small. Coupler When IF & gt; 0, the corresponding IC is essentially independent of VCE under certain IF effects. The linear relationship between IC and IF changes, and the output characteristics of the coupler measured with the semiconductor tube characteristic plotter are similar to those of the normal transistor output characteristics.
3, the coupler can be used as a linear coupler
In the light-emitting diode to provide a bias current, and then the signal voltage through the resistance coupled to the light-emitting diode, so that the phototransistor is received in the bias current increase and decrease the optical signal, the output current will be with the input signal The voltage changes linearly. Coupler can also work in the switch state, transmission pulse signal. In the transmission pulse signal, the input signal and the output signal between the existence of a certain delay time, different structure of the coupler input and output delay time vary greatly.