these are P-mosfets instead of PNP
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if you need to do it with mosfets ,
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Wouldn't you want to add a pull-up resistor from the NPN collector to + to help with noise on the base of the PNP?
I think it's ok. I'd suggest, however, to replace R8 by a 5-fold larger value than R7, in order not to reduce the gate driving voltage unnecessarily at 12V operation voltage. This also guarantees, that the max. Vgs of -20V won't be exceeded at 24V operation. For 28V operation - if necessary -, use a 12..18V Zener diode in parallel to R8.
A MOSFET only needs drive current during switching, not during its "on" state. Saves driver power from the ULN array.What are the pros and cons of using MOSFET over PNP?
Your 80kHz requirement shouldn't give a problem; the max. load current depends on your heat transfer capability. Without additional heat sinking, see e.g. IRF9530's max. allowed drain current vs. its case temperature, Fig. 9 in International Rectifier's data sheet.Will you please comment about output frequency we can give and maximum load current we can promise here.?
I think it's ok. I'd suggest, however, to replace R8 by a 5-fold larger value than R7, in order not to reduce the gate driving voltage unnecessarily at 12V operation voltage.
This also guarantees, that the max. Vgs of -20V won't be exceeded at 24V operation. For 28V operation - if necessary -, use a 12..18V Zener diode in parallel to R8.
the max. load current depends on your heat transfer capability. Without additional heat sinking, see e.g. IRF9530's max. allowed drain current vs. its case temperature, Fig. 9 in International Rectifier's data sheet.
Also, a MOSFET array - if available - probably will fail because of the restricted heat transfer possibility.
1-R7 good , R8 can be higher , 10K or something (as far as i know ) plz check in your isis simulator
2- the mosfets in general are better than bipolar transistors for higher current applications , they dissipate less heat ( beacause of lower resistance and voltage drop ) and approximatly zero current at base ( gate ) because they are voltage controlled devices . but for low current <1-2A i prefer bipolar since they are easier to drive and more robust to transients and safer for handling ESD .
hope that helps
regards
I'd suggest to use a 15V Z-Diode. Even better gate drive voltage for your IRF9530.
Yes, but this is the absolute (w.c.) max. current without additional cooling. Results in a junction temperature of 100..125°C.Can we recommand 2A load current without heat sink or more?
For octal high side drivers I only know bipolar ones (but so what). E.g. MICREL MIC2981/2982 , up to 350mA.Thanks for the [array] info, but not even for lower load current like 500mA..??
With the Z-Diode solution, the 30V capability, and considering the ¼W limitation, you'd have to choose new resistor values for R7 & R8. Pls. see below!I have gone for 680 ohms for R8, is it fine considering operation for 5-30VDC.
Again in ISIS simulator it gives the 30mA branch current for branch R8. So how much wattage rating required here for both R7 and R8.? Do i need to go for R8 = 10K considering 5-30VDC? We have in our inventory normally 1/4 watt (1206 smd or leaded) resisters.
For > 10kHz operation you should use an appropriate Schottky diode instead of D2 (1N4007), because the latter one isn't fast enough to properly cut down the switch-off voltages from an inductive load.
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