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Figure 62. Speed of Response - Programming Down
Since up-programming speed is aided by the conduction of the series regulating transistor, while
downprogramming normally has no active element aiding in the discharge of the output capacitor, laboratory
power supplies normally program upward more rapidly than downward. In many Agilent laboratory power
supplies, however, a special transistor circuit provides for the more rapid discharge of the output capacitor for
downprogramming. With this circuit and the unstrapping of the major portion of the output capacitance, these
laboratory power supplies have up and down programming speeds in the order of 1ms.
High performance bipolar power supply/amplifiers provide ultimate performance in high speed programming
operation, with programming speed at least an order of magnitude faster than can be achieved with any standard
power supply with reduced output capacitance.
More details on these versatile supplies are given in the Principles of Operation Section.
Supplies using SCR preregulator circuits cannot, in general, be expected to respond as rapidly as shown in
Figures 61 and 62, since a change in output voltage must be accompanied by a change in rectifier voltage; the
large value of the rectifier filter plus protection circuits within the SCR preregulator prevent the rectifier
voltage from changing rapidly.