[geeks] (a) FETs? (b) current Wien bridge?

[der Mouse]

(a) I'm a dabbler in electronics, and find myself wanting to play with
FETs.  (I'm used to BJTs, but - see below - would find some FETs
convenient to have.)  As I understand it, there are basically four
kinds of FET ({n,p}-channel {depletion,enhancement}-mode), but I don't
consider my understanding anywhere near complete, so I know if there
are any other aspects I should be considering, and in any case I don't
know any numbers for small general-purpose ones.  Loosely put, I'm
looking for FET versions of the 2N3904/2N3906, if that helps -
through-hole parts costing a few cents each when buying quantities in
the few-hundred-to-a-thousand range.  Suggestions?

(b) I wanted to build an oscillator that ran in the neighbourhood of
400KHz and produced a moderately clean sine wave.  This is not
conceptually difficult, but most of the circuits I found for such
things are based on opamps, and I found the only opamps I have at ready
hand are 741s, whose gain drops with frequency, reaching 1 somewhere
near 1MHz - fine for the sort of audio stuff I've been playing with in
the past, but not for this.  So I started to build a circuit with
discrete parts, and looked into oscillator circuits.  The most
plausible circuit I found was the Wien bridge, but it is based on a
voltage amplifier, and the BJTs I have are current amplifiers, not
voltage amplifiers (see item (a)).  So I set myself the task of working
out a current-amplifier analog to a Wien bridge.  After an hour or so
of scribbling, I have something that should exhibit negative
resistance, but I haven't managed to convert it into anything
practical, much less anything practical which should oscillate.
Pointers, anyone?

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