How do I test a JFET for Zero Gate Voltage Drain Current on my curve tracer?
Zero Gate Voltage Drain Current - IDSS
What It Is:
Zero gate voltage drain current is the ID that flows when VDS is at a specified value and VGS=0.
On the curve tracer, the Collector Supply forces VDS and the gate is shorted to the source so that VGS=0V.
What The Display Shows:
The display shows VDS on the horizontal axis, and the resulting ID on the vertical axis. The specification is met when with VGS=0 and the specified VDS applied, ID is within the specified limits.
How To Do It:
1. Set controls:
A: Max Peak Volts to the lowest setting above the specified VDS
B: Max Peak Power Watts to the lowest setting that satisfies (ID x VDS)
C: Horizontal Volts/Div to display VDS between the 5th and 10th horizontal divisions
D: Vertical Current/Div to display ID between the 5th and 10th vertical divisions
E: Collector Supply Polarity to (+DC) for N-channel or (-DC) for P-channel)
F: Configuration to (Base/Short, Emitter/Common)
G: Variable Collector Supply to minimum % (full ccw)
H: DotCursor ON
2. Apply power to the JFET:
A: Position the Left/Right switch as appropriate
B: Slowly increase the Variable Collector Supply % until the specified VDS is reached
3. Compare to data sheet specifications:
Check that at the specified VDS, ID is within the specified limits
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