mosfet circuit modify

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
Hi,
The picture attached is an Arduino_Optocoupler_Mosfet control circuit, can I simply multiple Mosfets in parallel, say 4 of. Can the circuit 4 times large the current output?
Thanks
Adam
pp02.gif
 

AnalogKid

Joined Aug 1, 2013
9,257
Yes, BUT . . .

1. You would be better off and get more consistent performance if you use one large MOSFET rather than 4 small ones.

2. The circuit will place 24 V across the gate-source barrier. For most MOSFETs, this barrier is rated for a maximum of 20 V, and the FET is fully enhanced with less than 10 V. To fix this, add a resistor between the +24 V source and the optocoupler collector. If the two resistors are of equal value, such as 10 K, there will be just under 12 V on the gate; a nice, safe value.

ak
 

LowQCab

Joined Nov 6, 2012
558
It depends on how fast you need the MOSFETs to turn completely-On, and completely-Off.

The Gate of a FET is basically a Capacitor,
how fast can you charge, and dis-charge it.
.
.
.
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
Yes, BUT . . .

1. You would be better off and get more consistent performance if you use one large MOSFET rather than 4 small ones.

2. The circuit will place 24 V across the gate-source barrier. For most MOSFETs, this barrier is rated for a maximum of 20 V, and the FET is fully enhanced with less than 10 V. To fix this, add a resistor between the +24 V source and the optocoupler collector. If the two resistors are of equal value, such as 10 K, there will be just under 12 V on the gate; a nice, safe value.

ak
Thanks.
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
You can parallel MOSFETs, but you better know what you are doing.
Thanks.
actually I may have a silly question here, I attached a picture of IRF3205, that documented a 110A current handle in certain condition.
The IRF32025's pin size: s=0.55*1.4 ~0.77mm square, can it handle that much current?
 

sagor

Joined Mar 10, 2019
439
Thanks.
actually I may have a silly question here, I attached a picture of IRF3205, that documented a 110A current handle in certain condition.
The IRF32025's pin size: s=0.55*1.4 ~0.77mm square, can it handle that much current?
No, if you notice the little "5" in a circle beside the 110A in the datasheet, you can see that the package is limited to 75A due to the design of the package, and that assumes all other parameters are below maximum limits (like heat dissipation good enough to keep temps low)
https://www.infineon.com/dgdl/irf3205pbf.pdf?fileId=5546d462533600a4015355def244190a
 

Thread Starter

LAOADAM

Joined Nov 21, 2018
563
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