2n5486 replacment for 2n5457?

[Bigbizkit]

Hi guys, is it ok to replace a 2n5457 mosfet with 2n5486?
Building a guitar compressor but i couldnt find a 2n5457, i thought its ok to replace it with 2n5486....

[Groovenut]

Probably going to depend on the jfets function in the circuit. If it's a buffer, the 2N5486 will probably be fine. If it's an amplifier, chances are changes will have to be made to the circuit values to get it to work in a similar fashion. You'll want to take a look at the pinch off values on the spec sheets of the two parts and compare them.

[garcho]

Post a link to the schematic and look up the datasheets:

http://www.onsemi.com/pub_link/Collateral/2N5486-D.PDF

http://www.onsemi.com/pub_link/Collateral/2N5457-D.PDF

It's fairly difficult to ruin anything by simply swapping low power transistors (like the ones in guitar pedals) - even if they're the wrong ones; your circuit might not function properly but nothing will "fry". Just try it and see what happens. If it doesn't work...

...Groovenut is right, it depends on the circuit. There's a way to set up a JFET so that it can be used as a voltage-controlled amplifier. The voltage-controlled part is what can make swapping JFETs tricky. It depends on their "pinch off" or V_GS(off) range. According to those datasheets, the 5457 is -0.5V to -6V, but the 5486 is -2V to -6V. Ranges are given because the manufacturing process can't guarantee anything more accurate than that, which means each transistor can be and probably will be, slightly different. If the circuit you're putting together depends on the control voltage applied to the gate of that JFET, there is a chance your substitution won't work without adjusting other things.

You might know all this but some things to keep in mind:
There are BJT transistors, of which 2 varieties exist: NPN and PNP. Frequently, you'll find you can swap out most NPNs for another NPN. Swapping a PNP for a NPN or vise versa will not achieve what you want. Guitar pedals mostly use NPN but with a major exception being vintage-style "fuzz" pedals which tend to use PNP (also, they tend to be germanium transistors, another consideration).

There are JFET transistors, sometimes called "FET" of which 2 varieties exist: N-channel and P-channel. Again, you cannot exchange a N-channel for a P-channel, and vise versa. For the most part guitar pedals will have N-channel JFETs.

There is another type of FET called a MOSFET, which has two types: enhancement and depletion modes, each with N-channel and P-channel types. In guitar pedal world, we basically only use one type, the enhancement-mode N-channel.