Datasheet

LM7321, LM7322
www.ti.com SNOSAW8D –MAY 2008–REVISED MARCH 2013
Figure 66. −SR vs. Capacitive Load
The combination of these features is ideal for applications such as TFT flat panel buffers, A/D converter input
amplifiers, etc.
However, as in most op amps, addition of a series isolation resistor between the op amp and the capacitive load
improves the settling and overshoot performance.
Output current drive is an important parameter when driving capacitive loads. This parameter will determine how
fast the output voltage can change. Referring to the Slew Rate vs. Capacitive Load Plots (Typical Performance
Characteristics section), two distinct regions can be identified. Below about 10,000 pF, the output Slew Rate is
solely determined by the op amp’s compensation capacitor value and available current into that capacitor.
Beyond 10 nF, the Slew Rate is determined by the op amp’s available output current. Note that because of the
lower output sourcing current compared to the sinking one, the Slew Rate limit under heavy capacitive loading is
determined by the positive transitions. An estimate of positive and negative slew rates for loads larger than 100
nF can be made by dividing the short circuit current value by the capacitor.
For the LM7321/LM7321Q/LM7322/LM7322Q, the available output current increases with the input overdrive.
Referring to Figure 67 and Figure 68, Output Short Circuit Current vs. Input Overdrive, it can be seen that both
sourcing and sinking short circuit current increase as input overdrive increases. In a closed loop amplifier
configuration, during transient conditions while the fed back output has not quite caught up with the input, there
will be an overdrive imposed on the input allowing more output current than would normally be available under
steady state condition. Because of this feature, the op amp’s output stage quiescent current can be kept to a
minimum, thereby reducing power consumption, while enabling the device to deliver large output current when
the need arises (such as during transients).
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