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I'm trying to come up with a setup to make a three terminal sweep for transistors. I am able to program two 2400's to do a gate and source-drain sweeps but the gate current I'm reading from one of the 2400s is 2 orders of magnitude higher (microamps) than the value read by a parametric analyzer (tens of nanoamps). I read somewhere on this forum that 2400s (and BNC cables) are not suitable for these measurements due to low input impedance and I wonder if the high gate leakage current I'm getting is due to this issue.
I do have an electrometer (Ketihley 6514) and I wonder if I can combine it with the 2400's in the setup. The 6514 does not source voltages as far as I know, so I'm not sure how I can use it. Any help will be appreciated!
- Keithley Applications
- Posts: 1446
- Joined: October 15th, 2010, 10:35 am
- Country: United States
With no cable attached at all to the 2400, source the max gate voltage and measure the current. This would be your open circuit offset value.
Then connect your cable and connection to everything except your transistor and repeat. Do you get a much larger offset, perhaps due to leakage through the cable/test fixture?
The specs for the 1uA measure range is 0.029% + 300pA. Conditions of this spec are called out in the footnotes of the spec/datasheet. Use 1 NPLC speed setting and "properly zeroed" which basically means subtract the open circuit offset by use of the REL feature or subtract it yourself.
When was your instrument last calibrated?
The 6514 does not have voltage source; it could be used to measure the gate current while the 2400 sources voltage. However, it would require a custom cable to adapt the triax of the 6514 in series with the 2400 and the DUT connection.
NOTE: the 2450 is a technology refresh of the 2400 and has two lower current ranges than the 2400 and has native triax connectors on rear panel to give realistic chance of using the 100nA and 10nA range performance.
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