Using Digikey’s parameter selection system let’s spec the “ideal FET for this and similar applications. This will need a good heatsink if the load is on for more than a second or two, but it is no issue if it gets millisecond pulses every few seconds. Try taking the pulldown resistor off pin 7, that is just dragging down the output of the internal LED that turns the transistor on. Also easier if you need to do high side switching. Notify me of new posts via email. AFAIK a servo, even a 12volt one, needs a 5volt logic signal. At 8A it is not even breaking a sweat.

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Well what an amazing article. My hairs are starting to turn gray: Safer to keep the diodes on the board.

Using MOSFETS with TTL levels (5 Volt and 3.3 Volt)

What i like you to do first is to detach the pic-circuit and just put 5 Volt on the entrance of yr FET circuit, via say that ohm resistor, and see if then your lamp behaves the same. IRFZ44, and you want to switch somewhat higher voltages i.

You could consider the FQP27P In my schematic I use an output with a small resistor Ohms in series with the gate of the N Channel Mosfet STP3NA and my load is in drain like the first schematic showed in this post, but I have no R1 resistor between gate and source, I only have a resistor like R1 in the second schematic.


That is definitely enough for most applications. As far as the microcontroller is concerned, an optocoupler mosfdt just an LED.

I use Cat-6 for those low currents. Sign up or log in Sign up using Google.

opto isolator – Optoisolation and Mosfet combo – Electrical Engineering Stack Exchange

That’s not vast but unnecessarily takes voltage that could be being applied to the motor. Rds 38mOhm with a Vgs of 3. Please mosfft in mind that eventhough a logic level FET, the IRLN is not at its lowest resistance at 5 Volt, but it shld be low enough to make 10 amp no problem. Great, that is good to know.

The IRL is a logic level FET and putting 5 4n53 on the gate should be enough to open it up, albeit that it has a drain source resistance of less than one ohm, though that depends a bit on the current and the temperature.

The solution is to change to a p-channel FET. Leave a Reply Cancel reply Enter your comment here Yes you can make it Ohm.

Since I want to learn, I tried to redesign it again by adding another resistor for the voltage divider. I will try source a IRL A P-channel fet there only can pull up. Sign up using Email and Password. Russell McMahon k 9 This actually is used for heatedbed in 3D printers up to A. So based on your comment, I have redrawn the circuit. So, the bottom line is: But if it is working for you, that is good. Also, from the graphs, Ids changes with Vds, is it because of the channel shortening effect?


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Suggestions on how to drive a MOSFET – Page 5

Presumably what would have been readable to all viewers before is now gibberish for me and an unknown number of other users. Somehow Logic P channel mosfetsarent as plentiful.

The idea is that this will then be my first custom PCB which we’ll etch in the lab and then incorporate into my refurbishing of an old vintage radio.

This will not work. The two P-channel mosfet will be driven by transistors. The latter is not too significant but is unnecessary.