Thanks Patrick!
I know I can always get my head on straight aftert reading your post.
I have a MJE340 set up on the bench and it is solid as a rock.
I had noticed that ARC used FET's and thought I might be missing something
there.
I still want to try the FET and make some test befor I commit to a PCB.
Thanks Again
RonL



"Ian Iveson" wrote in message
. uk...
I have used STD1HNC60 but I notice they have been discontinued by RS. I
recall low capacitance with decent transconductance were key
considerations.

The smaller the better, probably. Check out those with the lowest current
capacity and voltage limit you can get away with.

Keep in mind that your CCS must be stable, and work well beyond the
bandwidth of the amp. Patrick's presumably static measurements are not
worth much.

cheers, Ian

wrote in message
...
I'm wanting to use a FET as a current sink for a differential longtail.
This will be a balanced input front end using a 6922 with about a -60VDC
on the tail.
All the FETS I have around here seem to have the reverse protection diode
built in.
Can anyone recommend a good part number for this? I've been experimenting
with
the MJE350 bipolar part, but I want to try the FET and see if it will be
more stable
with temp and better PSRR. Any ideas appreciated.

Thanks!
RonL