Agilent Technologies 4338B, Service Manual

Page: 37 / 58

Analog Section
Figure 4-3 shows the analog section block diagram. The 4338B analog section can be divided
in six sections , the signal source , range resistor , current sense amplier , voltage sense amplier ,
process amplier , and dry circuit loop .
The signal source generates a 1 kHz signal of which level is set from the keyboard or by GPIB
commands . The signal is applied to the range resistor and to the DUT via the High-Current
(H
CUR
) connector . The current owing through the DUT ows into the ground via the
Low-Current (L
CUR
) connector and outer shield of the H
CUR
connector .
The vector current owing through the DUT is measured by the current sense amplier in
terms of the vector voltage across the range resistor . The vector voltage across the DUT is
measured by the voltage sense amplier .
The process amplier selects one of the above two vector voltages . The selected voltage is
processed according to measurement conditions , such as signal source level and measurement
range , and is converted into digital data by the Analog-to-Digital Converter (ADC).
The dry circuit loop attains the dry circuit mode by limiting the signal source output, so that
the voltage across the DUT is not more than 20 mV.
Figure 4-3. Analog Section Block Diagram
T roubleshooting 4-5