Guest
Eeyore wrote:
edges through the Cgd's caused lock-up of one section, quickly
noticed by the others, nett result a few uS of chaotic transient
oscillations (and Cgd pumping) as they all settled into step. A few nH
of series strays didn't help either. A LF 'dominant pole' fixed the
problem but the setup was numb out beyond a few kc hence useless as a
'load'. Did the job at the time but would rethink next time round.
Yes. Fitted. The diodes only helped. Fast 30~40V, (external) incomingjohn jardine wrote:
[...]
Servo arrangement summat like this?.
http://img518.imageshack.us/my.php?image=eloadte9.png
[An 'electronic load' project (scrapped). Occasionally blew opamps
consequent to particular dynamics on the Red wire. Traced to Drain/gate
feedback transients coupled with slightly dissimilar current source slew
rates.]
Surely would have been fixable with a reverse biased diode from op-amp o/p to V+
and another one from the - i/p to ground, but you'd have needed a small series
R.
Graham
edges through the Cgd's caused lock-up of one section, quickly
noticed by the others, nett result a few uS of chaotic transient
oscillations (and Cgd pumping) as they all settled into step. A few nH
of series strays didn't help either. A LF 'dominant pole' fixed the
problem but the setup was numb out beyond a few kc hence useless as a
'load'. Did the job at the time but would rethink next time round.