Transistor Optocoupler CTR (Current Transfer Ratio) Calculator

This page provides a Transistor Optocoupler CTR (Current Transfer Ratio) calculator. It also explains the Optocoupler CTR formula or equation used in this calculator.

What is an Optocoupler?

Introduction: An optocoupler consists of an infrared LED and a phototransistor.

When a signal is applied to the infrared LED, it turns ON, and light falls on the phototransistor. As a result, the phototransistor starts conducting. Importantly, there is no electrical connection between the LED and the phototransistor in the optocoupler.

Optocoupler CTR Formula

CTR is an important parameter used to measure the performance of an optocoupler. It is defined as the ratio of the output or collector current of the device (Ic) to the input current applied to the LED.

The equation above is used for Optocoupler CTR calculation. CTR is usually expressed as a percentage.

Optocoupler CTR Calculator

The following calculator can be used to calculate the CTR (Current Transfer Ratio) of a transistor-based optocoupler.

Example of Optocoupler CTR Calculation:

• INPUTS:

  • Ic (Collector Current or Output Current) = 10 mA
  • Input Current (If) = 5 mA

• OUTPUTS:

  • CTR = 2 or 200%