AD817AR Analog Devices Inc, AD817AR Datasheet - Page 11

• Manufacturer Part Number: AD817AR
• Description: IC OPAMP HS LP 8-SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD817AR

• Slew Rate: 350 V/µs
• Mounting Type: Surface Mount
• Rohs Status: RoHS non-compliant
• Applications: General Purpose
• Number Of Circuits: 1
• -3db Bandwidth: 50MHz
• Current - Supply: 7mA
• Current - Output / Channel: 50mA
• Voltage - Supply, Single/dual (±): 5 V ~ 36 V, ±2.5 V ~ 18 V
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• No. Of Amplifiers: 1
• Bandwidth: 50MHz
• No. Of Pins: 8
• Settling Time: 70ns
• Operating Temperature Max: 85°C
• Peak Reflow Compatible (260 C): No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

REV. B
A HIGH PERFORMANCE ADC INPUT BUFFER
High performance analog to digital converters (ADCs) require
input buffers with correspondingly high bandwidths and very
low levels of distortion. Typical requirements include distortion
levels of –60 dB to –70 dB for a 1 volt p-p signal and band-
widths of 10 MHz or more. In addition, an ADC buffer may
need to drive very large capacitive loads.
The circuit of Figure 36 is useful for driving high speed convert-
ers such as the differential input of the AD733, 10-bit ADC.
This circuit may be used with other converters with only minor
modifications. Using the AD817 provides the user with the op-
tion of either operating the buffer in differential mode or from a
single +5 volt supply. Operating from a +5 volt power supply
helps to avoid overdriving the ADC—a common problem with
buffers operating at higher supply voltages.
SINGLE SUPPLY OPERATION
Another exciting feature of the AD817 is its ability to perform
well in a single supply configuration. The AD817 is ideally
suited for applications that require low power dissipation and
high output current and those which need to drive large capaci-
tive loads, such as high speed buffering and instrumentation.
Referring to Figure 37, careful consideration should be given to
the proper selection of component values. The choices for this
particular circuit are: R1+ R3//R2 combine with C1 to form a
low frequency corner of approximately 300 Hz.
500mVp-p
COMMON
MAX
V
Figure 36. A Differential Input Buffer for High Bandwidth ADCs
IN
+5V
–5V
CABLE
COAX
50
100 F
25V
100 F
25V
52.5
+V
–V
S
S
1k
1k
–11–
3
2
2
3
Combining R3 with C2 forms a low-pass filter with a corner
frequency of 1.5 kHz. This is needed to maintain amplifier
PSRR, since the supply is connected to V
divider. The values for R
the AD817’s exceptional output drive capability. In this con-
figuration, the output is centered around 2.5 V. In order to
eliminate the static dc current associated with this level, C3 was
inserted in series with R
AD817
AD817
V
IN
1k
–V
1k
+V
–V
+V
0.1 F
4
4
7
7
S
Figure 37. Single Supply Amplifier Configuration
S
S
S
C2
0.1 F
0.1 F
0.1 F
0.1 F
0.1 F
C1
6
6
R2
10k
R1
9k
R3
1k
L
L
.
2
3
and C
AD817
26
27
+V
V
ADREF43
REFERENCE
V
7
4
INA
VOLTAGE
S
INB
AD773
18MHz
10-BIT
+2.5V
ADC
L
0.01 F
3.3 F
were chosen to demonstrate
6
0.1 F
150
C3
IN
R
L
SELECT C1, R1, R2 & R3
FOR DESIRED LOW
FREQUENCY CORNER.
(R2 = R1 + R3)
through the input
AD817
C
C
200pF
OUT
L
V
OUT