Datasheet

AD8397
Rev. A | Page 12 of 16
CAPACITIVE LOAD DRIVE
When driving capacitive loads, many high speed operational
amplifiers exhibit peaking in their frequency response. In a
gain-of-two circuit, Figure 23 shows that the AD8397 can drive
capacitive loads up to 270 pF with only 3 dB of peaking. For
amplifiers with more limited capacitive load drive, a small series
resistor (R
S
) is generally used between the amplifier output and
the capacitive load in order to minimize peaking and ensure
device stability. Figure 24 shows that the use of a 2.2 Ω series
resistor can further extend the capacitive load drive of the AD8397
out to 470 pF, while keeping the frequency response peaking to
within 3 dB.
5
0
–5
–10
–15
–20
–25
–30
–35
–40
0.01 0.1 1 10 100
05069-021
FREQUENCY (MHz)
GAIN (dB)
220pF
100pF
270pF
150pF
Figure 23. Capacitive Load Peaking Without Series Resistor
5
0
–5
–10
–15
–20
–25
–30
–35
–40
0.01 0.1 1 10 100
05069-030
FREQUENCY (MHz)
GAIN (dB)
470pF
390pF
330pF
270pF
Figure 24. Capacitive Load Peaking with 2.2 Ω Series Resistor