can you have a look and let me know if the following circuit will work.View attachment 69046
ive tried to simplify the diagram a bit, i am driving 360 multiplexed leds, and just wanted to check the way i have the mosfets set up. and if the transistor arrangement i have used will drive the mosfets on. thanks in advance
i am only using 2 shift registers i just drew in one set of top and bottom so it was clearer for people to see how i wanted to connect the transistors to the mosfets. i will have 2 unused outputs on both registers. also i only drew 1 set of 36 leds there are infact 10 sets of 36 leds, this is for some outside tree lights on 200' of cable , the leds fit into pingpong balls as defusers.
hmm i didnt make that very clear!!! what i meant to say was all 360 leds are driven from 2 registers so at any one time there will be a min 10 leds lit
Why bother with the emitter follower between U2 and Q3? The emitter follower can only pull Q3's gate to U2's Vdd - 0.65V. Since Q3 is a logic-level NFET, you could just connect the U2 pin to the gate of Q3.
If the Vdd of U1 is 12V, then you don't need the inverter between U1 and the gate of Q1. If it is not 12V, then you need the inverter as a level shifter.
hi mike, the VDD of U1 is 5v. I left loads out of the drawing for simplicity but in doing so you dont get the full picture! i will post a full drawing later
hi alex can you please explain why its only 4.3v. it isnt working in sim but i dont understand why?? i thought if the collector of Q4 was 12v then the gate of Q3 would be 11.3v.
looks like i have been thinking incorrectly!! i had assumed as it was a bipolar transistor then the base voltage wouldnt have an effect on the emitter voltage i have changed it as you have sugested but still dosnt work in sim so i will have to wait a couple of days untill the parts get here so i can bread board it thanks for the help much appreciated
thanks alec i am using proteus and i think the p chanel mosfets are not working correctly in the sim. once the kids are in bed i will try again. only using the sim untill the parts arive! could you explain what antiphase means please
many thanks!
BTW i was in Cardiff not so long back!!! man there are some great pubs!! i have a mate that lives on the huge council estate there! talk about rabitt warren