- Mon May 04, 2015 4:50 pm
#16503
plggy wrote:I thought because it had a threshold voltage of 2-4v that I would be good at 3.3v.
No, it's not. It will start to turn on anywhere between 2V and 4V. At which exact voltage it will turn on depends on temperature, deviations of the manufacturing process and other factors. So you should not assume that the transistor will turn on below 4V.
plggy wrote:Also, why does it work with the LED but not with the larger load? Does the current required to switch increase with the load?
The mosfets resistance (R_DS(on)) depends on the gate-source voltage (V_GS). In your case V_GS is very low, so R_DS will be high, probably to high for your motor to turn on. The LED requires a much lower current (common LEDs will turn on at 1-2mA), so the voltage drop across the transistor is much lower.
plggy wrote:What about this one - http://www.irf.com/product-info/datashe ... 060pbf.pdf ?
It lists the Vgs(th) (Max) at 2.5V @ 25µA. Won't I burn it out at 3.3v?
As explained above, you always want to exceed V_GS(th) max, since the transistor is not guaranteed to be conducting below this voltage. V_GS max is +/-16V for this transistor, so it won't burn out. But the IRLML2060 has a rather high R_DS(on), so it's not your best choice. It probably will get hot (see Fig. 2).
A better choice would be this one:
http://www.irf.com/product-info/datashe ... rlz24n.pdf