6241A/6242 DC Voltage Current Source/Monitor Operation Manual
5.1.3 Preventing Oscillation
5-5
5.1.3.2 Oscillation from the Device Itself
The device itself may oscillate due to the stray capacitance of cables and test fixtures. 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 filter near the device as in Figure 5-4.
• For transistors it is effective to attach a ferrite filter at the base and for FETs at the gate.
• To minimize a current leak, be careful that a ferrite filter does not touch other terminals, the device
case, lead wires, or other ferrite filters.
Figure 5-4 Preventing Device Oscillation
• For a high frequency device such as a GaAS FET, take the following measures.
• Separate the ground line of gate power supply from that of drain power supply.
• Insert ferrite filters and a by-pass capacitor both at the gate and drain so that high frequency sig-
nals do not go into the power supply.
• Insert matching resistors both at the gate and drain or make the pattern length λ/4 for matching.
Figure 5-5 6241A/6242 Oscillation Countermeasures
Ferrite filter
Shield Box
(Note) Insert a resistor with a value in a tolerable range.
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