| Electronics > Beginners |
| use bjt or mosfet in h-bridge with inductive load? |
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| alireza7:
hi is it better to use 2 pnp bjt in high side and 2 npn bjt in low side of an inductive load drive h-bridge ? or using 2 pmos in high side and 2 nmos in low side of h-bridge? what are the advantages and disadvantages of using each one ? if our system is intended to drive a particular inductive load continuously for 10 years with switching frequency below 50Hz, which one seems to be more reliable and durable? |
| JS:
What's the power level? Reliability depends a lot on the design, not only on the device. BJTs might seem more rugged as they don't have such a delicate part as the gate, but there are mosfet devices running for many years without problems, protect and drive propperly and you shouldn't have problems. Mosfets runs at loser temp, as a low rds on one will have way lower losses than a saturated. Bjt. JS JS |
| alireza7:
this is my schematic : i want to excite a (0.5H 200OHM) load with +- 20ma; with switching frequency below 50Hz for protection i used two back to back 4.7v zener diodes connected to the load terminals as illustrated in my schematic . is this configuration of zener diodes a good way for protection? or i should use following configuration? |
| alireza7:
--- Quote from: blueskull on July 25, 2018, 05:52:57 am --- FETs are extremely reliable, as long as you know how to drive then properly. --- End quote --- can you please explain more ? i would be appreciated for any schematic . |
| alireza7:
--- Quote from: blueskull on July 25, 2018, 05:52:57 am ---If you put clamping diodes across each BJT, then BJT can be as reliable as FETs. FETs are extremely reliable, as long as you know how to drive then properly. BJTs suffer from various issues, mostly related to SOA, both FBSOA and RBSOA. Adding clamping kinda gets rid of the RBSOA issue, and since it is used for power switching, FBSOA is naturally not an issue. For the sake of simplicity, I will go with BJT with diode. --- End quote --- in most bjt datasheets i just can find maximum rating of Collector −Emitter Voltage as a positive value and it seems that it's just corresponds to the positive voltages that one can apply to the Collector −Emitter. but what about negative Vce voltage which a bjt can tolerate? |
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