Datasheet
AD8510/AD8512/AD8513
Rev. H | Page 15 of 20
Figure 46 shows a scope plot of the output of the AD8510/AD8512/
AD8513 in response to a 400 mV pulse. The circuit is configured in
positive unity gain (worst case) with a load experience of 500 pF.
TIME (1µs/DIV)
VOLTAGE (200mV/DIV)
V
SY
= ±15V
C
L
= 500pF
R
L
=10kΩ
02729-041
Figure 46. Capacitive Load Drive Without Snubber
When the snubber circuit is used, the overshoot is reduced from
55% to less than 3% with the same load capacitance. Ringing is
virtually eliminated, as shown in
Figure 47.
TIME (1µs/DIV)
VOLTAGE (200mV/DIV)
V
SY
= ±15V
R
L
= 10kΩ
C
L
= 500pF
R
S
= 100Ω
C
S
= 1nF
02729-042
Figure 47. Capacitive Load with Snubber Network
Optimum values for R
S
and C
S
depend on the load capacitance
and input stray capacitance and are determined empirically.
Tabl e 5 shows a few values that can be used as starting points.
Table 5. Optimum Values for Capacitive Loads
C
LOAD
R
S
(Ω) C
S
500 pF 100 1 nF
2 nF 70 100 pF
5 nF 60 300 pF
OPEN-LOOP GAIN AND PHASE RESPONSE
In addition to their impressive low noise, low offset voltage, and
offset current, the AD8510/AD8512/AD8513 have excellent
loop gain and phase response even when driving large resistive
and capacitive loads.
Compared with Competitor A (see
Figure 49) under the same
conditions, with a 2.5 kΩ load at the output, the AD8510/AD8512/
AD8513 have more than 8 MHz of bandwidth and a phase margin
of more than 52°.
Competitor A, on the other hand, has only 4.5 MHz of band-
width and 28° of phase margin under the same test conditions.
Even with a 1 nF capacitive load in parallel with the 2 kΩ load
at the output, the AD8510/AD8512/AD8513 show much better
response than Competitor A, whose phase margin is degraded
to less than 0, indicating oscillation.
FREQUENCY (Hz)
GAIN (dB)
10k
–30
–20
–10
100k
0
10
30
1M 10M
50M
40
50
20
60
70
–135
–90
–45
0
45
90
135
180
225
270
315
PHASE (Degrees)
02729-043
V
SY
= ±15V
R
L
= 2.5kΩ
C
L
= 0pF
Figure 48. Frequency Response of the AD8510/AD8512/AD8513
FREQUENCY (Hz)
GAIN (dB)
10k
–30
–20
–10
100k
0
10
30
1M 10M
50M
40
50
20
60
70
–135
–90
–45
0
45
90
135
180
225
270
315
PHASE (Degrees)
02729-044
V
SY
= ±15V
R
L
= 2.5kΩ
C
L
= 0pF
Figure 49. Frequency Response of Competitor A