Hi Jay_Diddy_B,
I was once again going through some topics that deal with "Electronic Loads"
As far as I can tell, your explanation is excellent!
As I myself use a faster Electronic Load(Jim Williams Design) for some tests, and you have also fitted your design with a faster opamp but that did not bring much faster edges.
Which I therefore think is too little current available to drive the Gate impedance fast enough.
Would it make sense to use e.g. an LT1010 as a buffer with a faster opamp to get a real jump in the edge speed?
The opamp used does not see a load when using the LT1010 and the LT1010 has a good drive capability for capacitive loads with its 7 Ohm output resistor.
Then to make it optimal, the gate resistance can be lowered a bit because the LT1010 already takes care of this for a large part.
A nice opamp with a lot of phase margin is the ADA4625 and this one also has inputs that includes V-
I am aware that these parts cost a bit more, but going out for dinner with your family costs a lot more and you usually forget about it after a few weeks :-)
Is it possible that you could test this once in LTSpice if you have the time?
My skills with LTSpice are not very good yet.
Building a test circuit now would be even faster for me :-)
I use this Active Load when I need fast edges.
Here is the above diagram in a box.
The Active Load is only used for speed testing and not for long time dissipating for much power.
I can mount a heatsink against the bottom as needed to dissipate some more.
For anyone working with fast or basically all Active Loads, twist your cabling between the source to be tested and the Active Load.
With the Jim Williams version as I showed above, every mm of wiring between the Active Load and the source is suspect if you want neat edges.
For anyone working with fast or basically all Active Loads, twist your cabling between the source to be tested and the Active Load.
With the Jim Williams version as I showed above, every mm of wiring between the Active Load and the source is suspect if you want neat flanks.
Thank and kind regads,
Bram