UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - High side high voltage MOSFET switching with 3V logic drive?

Martin G7MRV · 22nd Jan 2019, 11:57 pm

Actually, now I think about it, perhaps the opto-couplers are the way to go? Easy to drive from logic, good isolation, small package size, and amazingly cheap. Just seen 20x PC817s on the slow boat from the orient for a quid, 80v Vce. Might be right on the limit for the top voltage selection, but the current through them would be minimal.

These are bipolar of course, but would the junction voltage drop make any real difference in this case? The ends of the divider chain go to presets used to adjust the highest and lowest voltages, perhaps I could just make a slight adjustment that had minimal effect on the filter tuning.

I could probably shoehorn 18 optoisolators into the space left by one of the removed modules, plus the logic chips and the PIC uP, leaving the other modules space for the relay and power supply...

(found 100x PC817 optocouplers for under £2! so ive bought them anyway!)

22nd Jan 2019, 11:57 pm	#6
Martin G7MRV Heptode Join Date: May 2008 Location: Selby, North Yorkshire, UK. Posts: 951	Re: High side high voltage MOSFET switching with 3V logic drive? Actually, now I think about it, perhaps the opto-couplers are the way to go? Easy to drive from logic, good isolation, small package size, and amazingly cheap. Just seen 20x PC817s on the slow boat from the orient for a quid, 80v Vce. Might be right on the limit for the top voltage selection, but the current through them would be minimal. These are bipolar of course, but would the junction voltage drop make any real difference in this case? The ends of the divider chain go to presets used to adjust the highest and lowest voltages, perhaps I could just make a slight adjustment that had minimal effect on the filter tuning. I could probably shoehorn 18 optoisolators into the space left by one of the removed modules, plus the logic chips and the PIC uP, leaving the other modules space for the relay and power supply... (found 100x PC817 optocouplers for under £2! so ive bought them anyway!) __________________ I got food in ma belly and a license for ma telly My Blog - http://g7mrv.blogspot.com Last edited by Martin G7MRV; 23rd Jan 2019 at 12:09 am.