back to constructing my own

2 test jig:




I decided to build a test jig to see what the performance was like with a single MOSFET/resistor. I specifically
needed to know what the gate voltage range was going to be for a given amount of current.

I drilled and tapped a piece of scrap heat sink, and bolted down the STE and resistor, being a bit generous with
the heat sink compound. For ease of assembly (and a bit of physical durability) I used a terminal strip to tie
into, rather than just wiring everything together point-to-point. I also added spade lugs for easier assembly.
I decided to go with a 10 turn 2k helipot as the gate voltage source, for precision adjustment. I assume once
I hit the minimum gate voltage, current flow through the STE will be very sensitive to small increases in gate
voltage.

I used a separate power supply for the gate voltage, so that voltage drops in the load supply (due to resistive
losses under increasing current) wouldn't affect the gate voltage supply. The helipot was supplied with 13.0
volts from end to end. This STE started noticeably conducting at Vg = 3.42 volts, and passed 15A at 3.57 volts,
so a 0.15 volt increase on the gate translated to a 15 amp pass at 13.8 volts on the load supply.

At 30v load, the current draw accelerates on its own around 5 amps, and rapidly ran away until it hit the 10
amps I had set for the current limit on the PS. So it's going to require some negative feedback on the dial. That
needs to be more of a current adjustment than a gate voltage adjustment.



test jig layout:


test jig schematic:



highest resolution images
last updated 06/01/2025 at 22:23:50 by make_www_index.command version 2025.05.20.B