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1 - General Information
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If the output voltage exceeds either the positive or negative overvoltage set point, the output will shut
down and be disabled, automatically opening the output and sense relays. This leaves the output in a
high-impedance state.
The full ±512.5 milliampere output current is available only in voltage priority mode. In this mode, the
output voltage should be programmed to the desired positive or negative value. A positive current limit
value should also be programmed. Note that the negative current limit tracks the positive current limit set
point. The output will regulate at the desired voltage level, provided that the current limit has been set
higher that the actual output current requirement of the external load. Note that if the current limit is set
to a value between zero and 75 µA, the actual current limit will be ±75 µA. Thus, it is not possible to
program current limit values less than 75 µA in voltage priority mode. (This limitation does not apply in
current priority mode.)
Current Priority Operation
Each Agilent N3280A output is a four-quadrant bipolar dc source that can be operated in either voltage
or current priority mode. In current priority mode the output is controlled by a bi-polar constant current
feedback loop, which maintains the output current (source or sink) at its programmed setting. The output
current will remain at its programmed setting as long as the load voltage remains within the positive and
negative voltage limits. The voltage limits are not programmable and vary somewhat with the output
current. When the output current is zero, the voltage limits are typically ±10.75 V.
Figure 1-2 shows the current priority operating characteristics of the dc source. The area in quadrants 1
and 3 shows the characteristics of the unit when it is being operated as a source (sourcing power). The
area in quadrants 2 and 4 shows the characteristics of the unit when it is being operated as a load (sinking
power).
Output
Voltage
Output
Current
+ 0.5125mA
+ 10.75V
+
-
+
-
I setting
- 0.5125mA
+ 9.5V
+VL status set
Key
Sourcing power
Sinking power
Programmable
1
3
2
4
+ 12V
- 10.75V
-VL status set
- 12V
- 9.5V
-V limit
+V limit
Figure 1-2. Output Characteristic (Current Priority)