AD8045ARD Analog Devices Inc, AD8045ARD Datasheet - Page 17

• Manufacturer Part Number: AD8045ARD
• Description: IC OPAMP VF ULDIST LN 70MA 8SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD8045ARD

• Amplifier Type: Voltage Feedback
• Number Of Circuits: 1
• Slew Rate: 1350 V/µs
• -3db Bandwidth: 1GHz
• Current - Input Bias: 2µA
• Voltage - Input Offset: 200µV
• Current - Supply: 16mA
• Current - Output / Channel: 70mA
• Voltage - Supply, Single/dual (±): 3.3 V ~ 12 V, ±1.65 V ~ 6 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width) Exposed Pad, 8-eSOIC. 8-HSOIC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Output Type: -
• Gain Bandwidth Product: -

THEORY OF OPERATION
The AD8045 is a high speed voltage feedback amplifier fabri-
cated on ADI’s second generation eXtra Fast Complementary
Bipolar (XFCB) process. An H-bridge input stage is used to
attain a 1400 V/µs slew rate and low distortion in addition to a
low 3 nV/√Hz input voltage noise. Supply current and offset
voltage are laser trimmed for optimum performance.
FREQUENCY RESPONSE
The AD8045’s open-loop response over frequency can be
approximated by the integrator response shown in Figure 63.
The closed-loop transfer function for the noninverting configu-
ration is shown in Figure 64 and is written as
where:
s is (2 πj)f.
f
equals 1 (0 dB).
DC gain is therefore
Closed-loop −3 dB bandwidth equals
The closed-loop bandwidth is inversely proportional to the
noise gain of the op amp circuit, (R
model can be used to predict the −3 dB bandwidth for noise
gains above +2. The actual bandwidth of circuits with noise
gains at or below +2 is higher due to the influence of other
poles present in the real op amp.
CROSSOVER
0
V
V
V
1
V
V
V
OUT
OUT
OUT
V
IN
IN
IN
OUT
is the frequency where the amplifier’s open-loop gain
/V
=
=
=
IN
(
(
f
R
R
=
CROSSOVER
G
f
F
CROSSOVER
2
R
+
+
π
G
Figure 63. Open-Loop Response
R
R
f
×
10
G
F
f
FREQUENCY (MHz)
)
)
CROSSOVER
s
+
×
2
(
R
π
G
×
R
+
G
f
CROSSOVER
R
×
F
F
(
100
R
+ R
)
G
V
+
G
IN
)/R
R
f
F
CROSSOVER
×
G
)
. This simple
R
G
V
= 400MHz
1000
OUT
Rev. A | Page 17 of 24
DC ERRORS
Figure 65 shows the dc error contributions. The total output
error voltage is
The voltage error due to I
To include the effects of common-mode and power supply
rejection, model V
where:
Δ V
conditions.
PSR is the power supply rejection.
C MR is the common-mode rejection.
Δ V
conditions.
V
os
S
CM
nom
is the change in the power supply voltage from nominal
V
V
is the change in common-mode voltage from nominal
OUT
OS
V
is the offset voltage at nominal conditions.
IN
=
(ERROR)
V
R
OS
S
nom
Figure 64. Noninverting Configuration
=
+
I
I
OS
−
B
B
R
+
–
I
Figure 65. Amplifier DC Errors
∆
PSR
S
B
as
+
V
R
R
S
V
S
G
R
OS
+
⎛
⎜
⎝
G
B
R
+ and I
∆
CMR
G
V
R
+
G
CM
R
R
F
R
F
B
F
⎞
+ ⎟
⎠
− is minimized if R
I
B
−
R
F
+
V
+
V
+
OS
OUT
V
OUT
⎛
⎜
⎝
R
–
G
–
R
AD8045
+
G
S
R
= R
F
⎞
⎟
⎠
F
||R
G
.