Question 3 Optocouplers are extremely useful devices. One of the main applicatio

Question

Question 3 Optocouplers are extremely useful devices. One of the main applications of optocouplers is to electrically isolate 2 or more parts of a cireuit. This serves a number of purposes for example it can be used to isolate sensitive instruments ground loop noise and switching noise in industrial settings. Read the datasheet "Optocoupler, Photodarlington Output, High Gain, with Base Connection" provided for the Vishay 4N32 and 4N33 series optocoupulers carefully and answer the following questions: 1. What is the maximum rated total power disspation of the device 2. What transistor configuration is used for the output of the device. 3. If the device is used to drive a counter for a digital signal in an indus- trial instrument, what is the maximum signal frequency for which the optocoupler may be used reliably

Explanation / Answer

1)The total maximum power dissipated can be found from the specification sheet as 250mW.It is given under total maximum powrer disspiated row.

2)The configuration is defenidefi Common emitter.Because in this output is collector terminal ,input is base terminal and emitter is common terminal.Given specification has load current as collector current.So output is at collector.Therefore Common emitter Configuration.

3)The Max.operating frequency is dependent upon turn on and turn off time.The signal should not change either when device is turning on or off.So the time taken to turn on is given as 5useconds which corresponds to frequncy of 1/5uSeconds=200kHz.And time taken to turn off is 100uSeconds so this corresponds to frequency of 1/100uSeconds =10kHz.Therefore Turn off time decides here the max frequency.Therfore maximum operating frequnecy foe reliable operation is 10kHz

Hope this helps.

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