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How to calculate the CTR of an optocoupler?
Following calculator is used to calculate CTR (Current Transfer Ratio) of an Optocoupler (Transistor based). EXAMPLE of Optocoupler CTR calculation : INPUTS: Ic (Collector Current or Output Current) = 10 mA, Input Current (If) = 5 mA OUTPUTS: CTR = 2 or 200%
How many milliamps can an optocoupler handle?
Typical optocouplers can handle input and output currents from a few microamps to tens of milliamps. There are many optocouplers on the market and to find the most appropriate for a particular purpose, vendor’s catalogues and manufacturers datasheets should be studied.
What kind of current does an opto coupler need?
As the current available from typical computer input/output ports may only be a few µA, as computer port lines are usually designed to drive some type of logic input, the input to this motor drive circuit is via a HCT Schmitt inverter gate, which only requires an input current of 1µA, with the 12V 40mA motor being driven by a 2N3904 transistor.
What is the voltage of an optocoupler gate?
Assuming that a single HCT output is only feeding this optocoupler, a logic 1 voltage of about 4.9V can be presumed. The output current available from a HCT gate to drive the optocoupler input is limited to 4mA, which is quite low for driving an optocoupler.
What kind of resistor does an optocoupler use?
The optocoupler infrared LED is driven at about 4mA via a 1kΩ resistor from IC1 output. As the CTR of the PC817 is around 115% the phototransistor can supply about 9mA as the supply to the phototransistor output is now taken from the 12V motor supply. This is more than the 5mA minimum required to drive the 2N3904 into saturation.
What kind of resistor do I need for a switching calculator?
For switching applications, a ¼-watt resistor with 5-% tolerance usually works fine. In order to use this calculator, you will need to know the input switching voltage (Vi), supply voltage Vcc, and the load current iL. Use the Standard Resistor Values chart to find the nearest standard resistor value.
How to calculate base resistance of a transistor?
Therefore, with simple transposition of the above formula, the following formula provides the base resistance: Rb = (Vi – Vbe) / Ib. To guarantee that the transistor operates in the saturation region, we multiply the base current by a factor of three.
How is the current transfer ratio ( CTR ) calculated?
Current Transfer Ratio (CTR) The current transfer ratio is a parameter similar to the DC current amplification ratio of a transistor (h FE) and is expressed as a percentage indicating the ratio of the output current (I C) to the input current (I F). CTR (%) = (I C /I F) x 100
What is the current transfer ratio in photocouplers?
Current Transfer Ratio (CTR) and Response Time of Photocouplers / Optocouplers Current Transfer Ratio (CTR) The current transfer ratio is a parameter similar to the DC current amplification ratio of a transistor (h FE) and is expressed as a percentage indicating the ratio of the output current (I C) to the input current (I F).
What does saturation mean for an opto isolator?
In the latter case the transistor is in saturation, this means the collector-emitter voltage across it is so low that the transistor is unable to further increase the current by changing its conductivity (due to more light from the LED). Thanks for contributing an answer to Electrical Engineering Stack Exchange!