Jim Thompson wrote:
On Mon, 14 Jan 2008 16:34:43 -0800, Joerg
wrote:

Jim Thompson wrote:
Not being a discrete MOS user, I am unfamiliar with what is currently
available.

I need NMOS and PMOS, VDS = 5V, ID =500uA

(And truly small... need capacitance as low as possible.)

Operating frequency = 100KHz

Suggestions?

Thanks!

So, what did you finally buy? Inquiring minds want to know ... :-)

And no, this time we won't ask what circuit you built.

I'm on hold while I await further experiments by the client, but it
certainly looks promising to use small MOS devices to cascode large
photodiodes into TIA's.


So far I've only once cascoded with a FET and back then it was ye olde
2N7002/BSS123 (but still followed with a BJT). Later only bipolar. Then
the fiberoptics part of my biz life became easier, lots of speed but
really low-C photodiodes.

I am sure you've read Phil Hoobs' paper but in case other haven't seen
it yet:

http://users.bestweb.net/~hobbs/frontends/frontends.pdf

For low-C work the newer dual-gate FETs are nice but I believe your
stuff is low frequency and I don't know how they behave down there
noise-wise. This would be the BF998 (they really messed up their links now):

http://www.infineon.com/dgdl/bf998se...1493688fd31042

--
Regards, Joerg

http://www.analogconsultants.com/