Please help to select MOSFET, or advise common MOSFET could be helpful in lab - Page 1
Forum section: electronics / beginners

author: sairfan1
author_rank: Frequent Contributor
timestamp: July 22, 2020, 07:26:04 pm
content: I want to turn ON some devices through MOSFET (SMD package preferred), some IC/MCU will be triggering MOSFET, can someone advise which MOSFET is suitable?To turn on ESP moduleTo turn on Dot matrix with 3mm LEDs 8x8 x 16To run 5/3v DC motors (those mostly found in toy cars)To trigger 5/3v Relay Module (switch)To turn on door lock relay 12/5v (it will be ON forever until someone open the door, and then back in ON mode)What do you suggest common MOSFET to be at lab for such experiments, or how can i find suitable myself? I will also buy some in DIP package to understand, do they have same part number for both kind of packages?

author: bob91343
author_rank: Super Contributor
timestamp: July 22, 2020, 11:01:40 pm
content: Look in the International Rectifier catalog. Then see how much they cost at a distributor.My source for this part has always been salvage parts from monitors or computers etc.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 23, 2020, 12:23:41 am
content: IRF540?Tim

author: eblc1388
author_rank: Frequent Contributor
timestamp: July 23, 2020, 12:29:47 am
content: How much voltage is available to drive the MOSFET?If 3.3V or less, you should probably looking for "logic level Mosfet" instead of the regular ones which needs more gate voltage than the MCU can provide.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: July 23, 2020, 05:41:25 am
content: For low to moderate power general purpose experimentation and projects my go-to mosfet is IRF3205 (IRF3205S in D2-pak) .It has very low on-state resistance so can handle lots of current without undue heating, and works well without a dedicated gate driver in most situations.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 23, 2020, 06:05:27 am
content: I recommend against using brick wall MOSFETs because 1. the low Rds(on) invites rather spectacular short circuit faults, and 2. the high gate charge and other capacitances makes the whole thing much slower than the user might at first expect. Even if the circuit isn't supposed to switch quickly anyway (e.g., just motor on/off, not PWMing), it can invite several kinds of parasitic behavior that a beginner is best to avoid.IRF540 is still kind of borderline in that regard, as it's strong enough to pull self-destructive fault currents. But a lesser version (IRF510 for instance) might not be strong enough for some loads. But hey, if it's getting hot, that might be a clue to put in a beefier one...Or there's BJTs, where the collector current is never more than hFE times the base current; hFE itself varies widely with manufacture and temperature, so it's not a great basis, but it gives you a ballpark at least. Whereas, MOSFETs just draw whatever they can while Vgs is "on", there's no feedback of sorts to the input side.Which if you're interested -- TIP31C (NPN) and TIP32C (PNP) are a good example, lowish hFE, 100V 3A rated. Because of the lowish hFE, it takes a fair current (100mA?) into the base, to switch a full load on the collector side; input current isn't something you have to worry about with MOSFETs.And yes, for logic compatible versions, shop for logic-level parts. For these families I think replacing F with L does it, e.g. IRL540? Downside, they're slower -- you have less voltage, to push around a somewhat higher capacitance. Again, fine for on/off stuff, and slow PWM.Tim

author: babysitter
author_rank: Frequent Contributor
timestamp: July 23, 2020, 06:26:38 am
content: Really, try the parametric search of distributors, then consult the datasheets of the resulting recommendations.BR babysitter