[sdiy] MOTM300 is an interesting design

[JH.]

> Rossum used a lot of dual FET buffers before JFET Op Amps came out, as did
> ARP. They can cause problems, so check the soldering and remove any flux
> from the PCB. I have been through quite a few 2n3958's whilst prototyping,
> so I now put them in 6pin DIL sockets.

I've seen high impedance opamp circuits from ARP, made from FETs (CD4007,
I think) and bipolar opamps. I'd say in most cases, this could be
substituted
by an off-the-shelf FET-input opamp with equal, or better, results.

But if you just have a FET pair, connected as source follower with Vgs
compensation,
it would be hard to beat in terms of _speed_.

JH.