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22nd June 2006, 05:50 PM
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 Pulsed collector current 4n33 optoisolator? The continuous collector current of a 4n33 is 150ma, If I vary the duty cycle to 50% can I double the current to 300ma? The application I have in mind is posted below.
__________________ Bill Home of the Firefly PIC Tutor Inchworm ICD2 http://www.blueroomelectronics.com Last edited by William At MyBlueRoom; 22nd June 2006 at 05:53 PM. | |
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22nd June 2006, 06:26 PM
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| 150 is the absolute max. I try to avoid designing to the maximum. also with Vsat at 1V, 300 mA at 50% duty cycle, you will see 150mW dissipation. This is the spec'd max also. I'd avoid it. why use an opto? you aren't getting isolation. why not just use a couple of transistors? | |
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22nd June 2006, 08:19 PM
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| Using optos gets me a nice isolation with the HV and I can mux the digit select with only 3 pins. I wonder if there are higher current optos out there?
__________________ Bill Home of the Firefly PIC Tutor Inchworm ICD2 http://www.blueroomelectronics.com | |
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22nd June 2006, 10:20 PM
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| unless there are more optos that aren't shown, you are only getting isolation on the 2 CA pins and none of the others. To me, isolation isn't a percentage thing - either you have it or you don.t. also, the power supply needs to be isolated. when I design isolated circuits, I create a "dmz" that has no electrical connections across it. including the power supply. Last edited by philba; 22nd June 2006 at 10:23 PM. | |
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22nd June 2006, 11:51 PM
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| You need driver transistors. The optos could drive two PNP transistors which would drive the display.
__________________ Len | |
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