I've seen various schematics and 1 thing I notice is that all MOSFETs used are N-channel. What other criteria should I be looking for?
I guessing it needs to be at least
Thanks!
I guessing it needs to be at least
- high current
- at least equal or higher to Vsupply (or 2x Vsupply if +/-)
Thanks!
I'm looking for generic specs that I should be looking for when selecting a part. as the specific device you're suggesting might not be available to me.
We want the mosfet with:
Minimal Rds on
Minimal Qg - Gate Charge should be less than 60Qg nC
Appropriate voltage rating
Minimal Rds on
Minimal Qg - Gate Charge should be less than 60Qg nC
Appropriate voltage rating
The relay (or FET's) can only see one rail or the other worst case, not both added together but as ever it is prudent to select one with a good margin. Many suitable FET's will be in excess of x2 of the total rail value anyway, even for amps running on high rails.
Low Rds (its on resistance) that @arthur mentions is one of the most important ratings for FET relay.
Low Rds (its on resistance) that @arthur mentions is one of the most important ratings for FET relay.
Eas > 500mJ
Qg<200nC as target (have used higher values without problems though)
Vdss = > 2x rail (safety margin)
To247 preferred over To220, while easier to have wider pcb traces. To247 bigger cross section of pins.
I’ve selected SUG80050E for my current project.
Qg<200nC as target (have used higher values without problems though)
Vdss = > 2x rail (safety margin)
To247 preferred over To220, while easier to have wider pcb traces. To247 bigger cross section of pins.
I’ve selected SUG80050E for my current project.
Gate charge is only relevant for high speed switching (not the case for speaker protection!). On resistance and blocking voltage are the key parameters - worth noting that some speaker loads are inductive enough to generate voltage spikes on sudden switch off - suggests either switch slowly (100's of microseconds) or have free-wheel diodes on the output of the relay connected to the amplifier rails.
If you drive the MOSFET gate with a photovoltaic isolator its worth checking the safe operating area of the FET when its interrupting its maximum fault current. Turn off with that kind of isolator can be quite slow. Alternatively use an active driver to remove the gate charge quickly.