Wednesday, July 11, 2018
building a JFET amp no math just logic
I'm going to piece together an audio amp to drive my Low Z earbud and my Hi Z earbud without any math other than in my head (guessing).
I selected the 2SK2539 simply because Arrow.com sells a 3000 reel for $15 dollars with free shipping. A reel should be a lifetime supply for an amateur. You can use whatever JFET you have on hand. The first step is to determine the Q point. I put a 1K resistor in the source circuit to set the bias and a 100k to tie the gate to the circuit. I wanted about 1 ma. This gave me just over 1 ma so far so good. The drain needs room to swing so I select a drain resistor that will drop about half the supply at 1 ma. 4.7K should work nicely. so ready for the next step.
Posted by Reset at 11:47 AM