Fast/Normal Operation; Inductive Loading; Capacitive Loading - Agilent Technologies 6631B User Manual

Fast/Normal Operation

A switch on the rear of the unit lets you switch between operating in either Fast mode or Normal mode.
When set to Fast mode, this switch disconnects the output capacitor that is located inside the unit. Fast
mode lets you improve or enhance certain operating characteristics; while at the same time degrading
other operating characteristics.
1. In Fast mode, the programming time for voltage programming is faster than for normal operation,
however, output noise is greater.
2. In Fast mode, the absence of the internal output capacitor results in increased output impedance and
therefore, greater stability when driving inductive loads. Conversely, the addition of external
capacitive loads in Fast mode will reduce the stability of the unit during constant voltage operation.
3. In Normal mode, the internal output capacitor helps control peak voltage excursions away from the
the nominal value for sudden changes in load current. In Fast mode, larger peak voltage excursions
will show up at the output of the unit during sudden load current changes.

Capacitive Loading

In Normal mode, the dc source will be stable for many load capacitances, however, large load
capacitances may cause ringing in the dc source's transient response. If this occurs, the problem may be
solved by increasing or decreasing the total load capacitance.
In Fast mode, the dc source can maintain stability only for small capacitive loads. These limits are:
Agilent 6631B
Agilent 6632B and 66322A
Agilent 6633B
Agilent 6634B

Inductive Loading

Fast mode is recommended for driving inductive loads, although you will typically experience stable
conditions in Normal mode. Inductive loads present no loop-stability problems in constant voltage
operation, but may cause problems in constant current operation if the load impedance is outside the
boundaries mentioned below.
The ratio of the load inductance (L) to the sum of the Equivalent Series Resistance (ESR) for the load
(R1) and dc source (Rs), determines whether the source can drive a load without becoming unstable. To
help determine this ratio, the value of Rs is listed as:
Agilent 6631B
Agilent 6632B and
66322A
Agilent 6633B
Agilent 6634B
If the ratio L/(R1 + Rs) is less than 0.005, the dc source can reliably drive the load.
2.2 µF.
1.0 µF.
0.22 µF.
0.10 µF.
0.1 ohm.
0.2 ohm.
1.0 ohm.
2.0 ohm.
Installation - 3
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