6240B DC Voltage Current Source/Monitor Operation Manual
5.1.3 Preventing Oscillation
5-5
5.1.3.2
Preventing DUT Oscillation
The DUT itself may oscillate due to the stray capacitance of cables and a test fixture. Particularly a high
h
FE
transistor or a high gm FET has a higher probability of oscillation.
Take the following measures to prevent oscillation.
•
Attach a ferrite bead near the DUT as in Figure 5-4
•
For the transistor it is effective to attach the ferrite bead at the base, and for the FET at the gate.
•
To minimize a current leak, be careful that the ferrite bead does not touch other terminals, the DUT
case, lead wires, or other ferrite beads.
Figure 5-4 Preventing DUT Oscillation
•
For a high frequency device such as a GaAS FET, take the following measures.
•
Separate the ground line of the gate power supply from that of the drain power supply.
•
Insert ferrite beads and by-pass capacitors both at the gate and the drain so that high frequency
signals do not enter the power supplies.
•
Insert matching resistors both at the gate and the drain or make the pattern length
/4 for match-
ing.
Figure 5-5 Preventing 6240B Oscillation
Ferrite bead
Shield box
(Note) Insert a resistor with a value in a tolerable range.
6240B
