I'm making an audio mixer circuit from Forrest Mims' Engineers' Mini notebook. He says to use the 2N3819 transistor. My local parts shop doesn't carry it. They have the BS107. Is that equivalent? What parameters should I be looking at anyway when searching for equivalents?

 

No, it's not equivalent. The 2N3819 is a depletion-mode JFET, and the BS107 is an enhancement-mode MOSFET-- a completely different animal. They are NOT interchangeable.

A good possibility as a replacement would be a 2N4416; like the 2N3819, it's designed for service as a VHF/UHF amplifier/mixer.

 

great, thanks!

 

Hello,

For refrence, the TS is taking about this schematic:



Bertus

 

For refrence, the TS is taking about this schematic:
View attachment 124965

I somehow missed the "audio mixer" part of the TS's query. For that application, I would probably choose a 2N5457.

 

I'm making an audio mixer circuit from Forrest Mims' Engineers' Mini notebook. He says to use the 2N3819 transistor. My local parts shop doesn't carry it. They have the BS107. Is that equivalent? What parameters should I be looking at anyway when searching for equivalents?

Most suppliers list the 3819 as discontinued - but you can still find them in a few places.

The 2 parameters you most need to get right is the gate cut off voltage and the zero gate voltage drain current.

Last time I checked; Farnell had the NS J113 that you might get away with - its not the Asian 2SJ113, that's a dirty great power FET.

The J113 was used in the DOD FET pre amp for guitars.

You can use a SS MOSFET as an amplifier, but the easiest way is to sense source current with a BJT and control the gate bias voltage.

 

Thanks guys, very much appreciated.