AD8051ART-REEL View Datasheet(PDF) - Analog Devices
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AD8051ART-REEL Datasheet PDF : 24 Pages
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APPLICATION INFORMATION
OVERDRIVE RECOVERY
Overdrive of an amplifier occurs when the output and/or input
range is exceeded. The amplifier must recover from this over-
drive condition. As shown in Figure 41, the AD8051/AD8052/
AD8054 recover within 60 ns from negative overdrive and
within 45 ns from positive overdrive.
INPUT 1V/DIV
OUTPUT 2V/DIV
VS = ±5V
G = +5
RF = 2kΩ
RL = 2kΩ
V/DIV AS SHOWN
100ns
Figure 41. Overdrive Recovery
DRIVING CAPACITIVE LOADS
Consider the AD8051/AD8052 in a closed-loop gain of +1 with
+VS = 5 V and a load of 2 kΩ in parallel with 50 pF. Figure 42
and Figure 43 show their frequency and time domain responses,
respectively, to a small-signal excitation. The capacitive load
drive of the AD8051/AD8052/AD8054 can be increased by
adding a low value resistor in series with the load. Figure 44
and Figure 45 show the effect of a series resistor on the capaci-
tive drive for varying voltage gains. As the closed-loop gain is
increased, the larger phase margin allows for larger capacitive
loads with less peaking. Adding a series resistor with lower
closed-loop gains accomplishes the same effect. For large
capacitive loads, the frequency response of the amplifier is
dominated by the roll-off of the series resistor and the load
capacitance.
8
6
4
2
0
–2
–4
VS = 5V
–6 G = +1
–8
RL = 2kΩ
CL = 50pF
–10 VOUT = 200mV p-p
–12
0.1
1
10
100
500
FREQUENCY (MHz)
Figure 42. AD8051/AD8052 Closed-Loop Frequency Response; CL = 50 pF
AD8051/AD8052/AD8054
VS = 5V
G = +1
RL = 2kΩ
CL = 50pF
2.60
2.55
2.50
2.45
2.40
50mV
100ns
Figure 43. AD8051/AD8052 200 mV Step Response; CL = 50 pF
10000
VS = 5V
≤ 30%
OVERSHOOT
1000
RS = 3Ω
RS = 0Ω
100
RG
RF
10
VIN
100mV
STEP 50Ω
RS
VOUT
CL
1
1
2
3
4
5
6
ACL (V/V)
Figure 44. AD8051/AD8052 Capacitive Load Drive vs. Closed-Loop Gain
1000
VS = 5V
≤ 30%
OVERSHOOT
RS = 10Ω
100
RS = 0Ω
RG
VIN
100mV
STEP 50Ω
RF
RS
VOUT
CL
10
1
2
3
4
5
6
ACL (V/V)
Figure 45. AD8054 Capacitive Load Drive vs. Closed-Loop Gain
Rev. H | Page 17 of 24
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