ADCMT 6253 - Preventing 6253 Oscillation; Preventing DUT Oscillation

6253 DC Voltage Current Source/Monitor Operation Manual
4.1.3 Preventing Oscillation
4-6
4.1.3.2 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 4-4.
• 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 sure that the ferrite bead does not touch other terminals, the DUT
case, lead wires, or other ferrite beads.
Figure 4-4 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 at the drain so that high frequency
signals do not enter the power supplies.
• Insert matching resistors both at the gate and at the drain or make the pattern length λ/4 for
matching.
Figure 4-5 Preventing 6253 Oscillation
Ferrite bead
Shielded box
R
HI OUTPUT
HI SENSE
LO SENSE
LO OUTPUT
DUT
(注) R は許容できる誤差範囲内の値を入れる。
R6243
6253
Note: Insert a resistor with a value in a tolerable range.