ADA4817-1 Analog Devices, ADA4817-1 Datasheet - Page 21

• Manufacturer Part Number: ADA4817-1
• Description: Low Noise, 1 GHz FastFET Op Amps
• Manufacturer: Analog Devices

Specifications of ADA4817-1

• -3db Bandwidth: 1.05GHz
• Slew Rate: 870V/µs
• Vos: 400µV
• Ib: 2pA
• # Opamps Per Pkg: 1
• Input Noise (nv/rthz): 4nV/rtHz
• Vcc-vee: 5V to 10V
• Isy Per Amplifier: 21mA
• Packages: CSP,SOIC

HIGH SPEED JFET INPUT INSTRUMENTATION
AMPLIFIER
Figure 53 shows an example of a high speed instrumentation
amplifier with a high input impedance using the ADA4817-1/
ADA4817-2. The dc transfer function is
For G = 1, it is recommended that the feedback resistors for the
two preamps be set to 0 Ω and the gain resistor be open. The
system bandwidth for G = 1 is 400 MHz. For gains higher than 2,
the bandwidth is set by the preamp, and it can be approximated by
In-amp
V
OUT
=
(
−3 dB
V
N
−
= (f
V
P
CR
V
V
)
N
⎛
⎜
⎜
⎝
P
× R
1
+
G
2
R
R
R
)/(2 × R
R
R
S1
S2
G
G
F
⎞
⎟
⎟
⎠
F
R
ADA4817-2
ADA4817-2
)
F
= 500Ω
U2
U1
R
V
V
V
F
V
CC
EE
CC
EE
= 500Ω
0.1µF
0.1µF
0.1µF
0.1µF
Figure 53. High Speed Instrumentation Amplifier
10µF
10µF
10µF
10µF
(16)
Rev. A | Page 21 of 28
350Ω
350Ω
R1
R3
350Ω
R4
Common-mode rejection of the in-amp is primarily determined by
the match of resistor ratios, R1:R2 to R3:R4. It can be estimated by
The summing junction impedance for the preamps is equal
to R
bandwidth response like in the previous example.
ADA4817-1
F
V
|| 0.5(R
V
CM
O
350Ω
V
V
R2
=
CC
EE
(
G
0.1µF
1
(
0.1µF
). Keep this value relatively low to improve the
δ
+
1
−
δ
1
δ
)
2
δ
)
2
10µF
10µF
ADA4817-1/ADA4817-2
V
O
(17)