EPC GaN fet tiles

Rds-on is so low on my parts, I'd need lots of amps to heat them up.

This might work:

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A quick test (using my Fluke on the diode range, 1 mA) suggests that the tempco of this sorta-diode is about -1.9 mV/K, so it's a usable thermometer.

The GaN parts behave like phemts. There's no actual substrate diode, but they turn on like gate-controlled e-fets when the drain goes negative.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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John Larkin
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I'm making 7ns HV pulses, and the time delay seems stable, to well under 1ns, so it can be removed in the generator.

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 Thanks, 
    - Win
Reply to
Winfield Hill

There's no silk on any of the pads. The BGA fets soldered nicely.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

A commonly cited number for the surface of the sun is about 6e7 w/m^2. My fet will only be about 2e6.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

Why only 10mA probe current? Even a 10 milliohm FET makes 10mV/amp, so, an amp for probing doesn't seem too bad. Pulsed, of course.

I sent you my hairball.

Cheers, James Arthur

Reply to
dagmargoodboat

The temperature is inferred by the voltage drop of the pseudo-substrate diode, when the source and gate are both zero volts and we pull the drain gently negative. More current then won't give more temperature signal. The fake-diode tempco is probably highest at low currents.

At 1 mA pulldown current (my Fluke on its diode range) I'm seeing about -1.6 volts on the drain of an EPC8004, and that drop has a tempco of close to 2 mV/K. That's a nice thermometer.

I'll adjust the 5 volt supply to set the ganfet power dissipation to around a watt maybe, and occasionally pulse the p-fet off to scope the temperature. The temp measurement could be very low duty cycle, say a millisecond of measurement every second or so.

Given a full millisecond to make the measurement, I could use 1 mA as the test current. I only need as long as it takes to charge the various capacitances.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

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