There are various types of optocouplers in optocoupler relays, including the following:

Transistor type optocoupler: composed of GaAs infrared LED and bipolar silicon phototransistor. The input electrical signal causes the LED to emit light, and the phototransistor receives the light and generates a photocurrent to achieve electrical optical electrical conversion. It has high conversion efficiency, high voltage resistance, and low input driving capability, with a medium speed and a current conversion ratio of 2% -120%. It is commonly used in general digital circuits and simple signal isolation and control, such as PC817, LTV817, etc.

Darlington transistor type optocoupler: It consists of two transistors that form a Darlington structure. The base of these transistors is controlled by an LED, providing high gain capability. It can be used for isolation in DC circuit related fields that require large driving capabilities. It has a medium speed and a current conversion ratio of 100% -600%, such as 4N32, 4N33, etc.

Diode type optocoupler: mainly composed of GaAs infrared LED and silicon photodiode, with the highest response speed but relatively low current conversion, ranging from 0.1% to 0.2%. It is commonly used in circuits that require extremely high speed, low signal transmission accuracy, and do not require significant driving power, such as signal isolation in high-speed data transmission.

Optocoupler SCR (silicon controlled rectifier): composed of GaAs infrared LED and silicon controlled rectifier, with a current conversion ratio greater than 100% from low to medium speed, used for control and isolation of AC related circuits, and can achieve control of high-power AC loads such as MOC3071, IL400, etc.

Optocoupler type TRIAC: composed of GaAs infrared LED and TRIAC, it can control AC loads from low to medium speed, such as the control of AC loads such as engines and solenoids. It is widely used in circuits that require control of AC signals, such as IL420, 4N35, etc., for AC dimming, motor speed regulation, etc.

Linear optocoupler: The structure consists of an infrared LED and an infrared receiving diode, and the output is a pure current signal. The input current has a linear relationship with the output current, and it has a linear output characteristic before the photodiode saturates. It is used in circuits that require precise transmission of analog signals, such as in some high-precision measuring instruments and analog signal isolation amplification circuits.

High speed integrated circuit output optocoupler: It has a receiving component that can provide high-speed integrated optical capability, with a speed of up to 1-10 megahertz, suitable for the transmission and processing of high-speed digital signals, such as signal isolation and transmission in high-speed data communication and high-speed logic circuits.