6243/44 DC Voltage Current Source/Monitor Operation Manual
4.1.4 Oscillation Prevention
4-7
4.1.4.2 Oscillation of the Device Itself
The device itself may oscillate due to stray capacitance from the leads or test fixture. The possibility of
oscillation is especially high for high hFE transistors and high gm FETs.
Prevent device oscillations taking the measures indicated below.
• Insert a ferrite bead near the device (Figure 4-5).
• Ferrite beads are effective when inserted at transistor bases and at FET gates.
• To minimize leak current, ensure that the ferrite bead does not contact other terminals, the device
case, lead wire, or the ferrite beads of other wires.
Figure 4-5 Device Oscillation Prevention
• For high-frequency devices such as GaAS FET, proceed as follows:
• Separate the ground lines of the gate source and the drain source.
• Insert a ferrite bead and a bypass capacitor in both the gate and the drain so that the high-frequen-
cy signal does not travel to the power source.
• Insert a matching resistor in both the gate and the drain, and match so that the pattern length be-
comes /4, etc.
Figure 4-6 SMU Oscillation Prevention
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