Hi Patrick,
I have found a cheap source of BF245C with IDSS 12-25mA. Could these be used in the SEN?
Well, I'm no expert, but I think that they would not be suitable because of their small transconductance ( 3-6.5 mS ), which means that SEN would have large input impedance. For example 2SK170 has 22 mS, and recommended 2SK369 40 mS - the higher the value, the lower the impedance.
But wait for Patricks answer, he certainly has much more knowledge than me
Wow, so 16 BF245's for 4 SK170's?
Perhaps I'll use a breadboard for a quick try and see approach.
I'll be using a DC supply so no worries on batteries.
What would the input impedance of the paralelled BF245's look like? Feasible to get below 5 ohms ?
I need a floating supply for another project. I have posted a floating supply here but i think this new one is more interesting because it is more symmetric. Also the CCS´s.
This is not dimensioned yet and i also think about alternative CCS´s so it shows only the principle at this moment. See one alternative.
This is not dimensioned yet and i also think about alternative CCS´s so it shows only the principle at this moment. See one alternative.
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This, with good trafos, should be a great alternative to batterie.
I found a cheap source of R-Cores locally and I´ll try some things with them. The R-Cores have two completely separate primaries, one on each spool. So I thought, this can make a perfect 1:1 isolation trafo. And it´s super efficient, it hardly warms up IME.
The other trick, to use it as a normal step down trafo, is to use one primary and one secondary, from different spools. Drastically reduce capacitive coupling between windings.
(I didn´t try this as of yet)
I found a cheap source of R-Cores locally and I´ll try some things with them. The R-Cores have two completely separate primaries, one on each spool. So I thought, this can make a perfect 1:1 isolation trafo. And it´s super efficient, it hardly warms up IME.
The other trick, to use it as a normal step down trafo, is to use one primary and one secondary, from different spools. Drastically reduce capacitive coupling between windings.
(I didn´t try this as of yet)
Here is the Mosfet version. Sure, your trick only works when you can use only one primary.
You could use one primary on 230V too but then you get the double output voltage. Using a transformer with half output voltage and you are back in business .....
You could use one primary on 230V too but then you get the double output voltage. Using a transformer with half output voltage and you are back in business .....
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The double CCS adds safety, in case you are using the mosfets. They can fail and pass much more current. (I have ruined a few playing on protoboard with low voltages, I´m not even sure how. Static?).
Altough not a big concern for the cascode CCS, if well soldered in place, which it will be of course.
Altough not a big concern for the cascode CCS, if well soldered in place, which it will be of course.
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