TCDT1102

Optoisolators - Transistor, Photovoltaic Output

TCDT1102 is an optoisolator, a device used to transfer signals from one circuit to another while electrically isolating the two circuits. It provides isolation between input and output circuits with a light signal path. This optoisolator features a photodiode optically coupled to a NPN, open-collector output transistor with photovoltaic transfer characteristics. By using this optoisolator, it isolates low voltage control systems from higher power and/or noisy environments, as it prevents the risk of ground loops and damage. It meets the needs for applications with safety considerations and performance requirements.

Application Field

TCDT1102 optoisolator is suitable for optical data transmission and signal coupling, which is often used in industrial applications. It has a wide range of uses, and some typical examples are listed below:

• Industrial controls with requirements of safety considerations and interference prevention.
• Driving of high voltage inductive or resistive loads under the control of a low voltage signal.
• Electrical isolation of analog and digital data transmission circuits and interference rejection.
• Isolation of signaling (transistor output) stages from the harsh environment of resistive or inductive loads.

Working Principle

The isolated photovoltaic output circuit consists of an infrared LED, a single photodiode and a NPN output transistor. The LED is driven by the input signal through the constant current source which provides a well-defined current; the LED is thereby turned on and off depending on the logic level of the signal. When the LED is turned on, the photodiode is subjected to the infra-red light output and a voltage, V, develops across the diode\'s terminals. This voltage is linearly proportional to the current of the LED. This voltage appears across the emitter and base junction of the output transistor, turning it on. Thus the current flowing through the load is proportional to the input current.

The mechanism of optical isolation prevents unstable operation caused by external noise. In addition, the optoisolator works as a voltage clamp providing over voltage protection. Thus, a stable, high input-to-output isolation that meets the isolation requirements of most safety standards, is achieved using the TCDT1102.

In conclusion, the TCDT303 can be used in applications with safety considerations and performance requirements due to its transistor, photovoltaic output design and protection mechanisms. Its applications span a wide range from industrial controls to analog and digital transmission with well suited features.