AD8066ARZ-R7 Analog Devices Inc, AD8066ARZ-R7 Datasheet - Page 24

• Manufacturer Part Number: AD8066ARZ-R7
• Description: IC,Operational Amplifier,DUAL,BIPOLAR/JFET,SOP,8PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Series: FastFET™r

Specifications of AD8066ARZ-R7

• Design Resources: Precision, Bipolar Configuration for the AD5426/32/43 8-Bit to12-Bit DACs (CN0036) Precision, Bipolar, Configuration for AD5450/1/2/3 8-14bit Multiplying DACs (CN0053)
• Amplifier Type: Voltage Feedback
• Number Of Circuits: 2
• Output Type: Rail-to-Rail
• Slew Rate: 180 V/µs
• -3db Bandwidth: 145MHz
• Current - Input Bias: 3pA
• Voltage - Input Offset: 400µV
• Current - Supply: 6.6mA
• Current - Output / Channel: 30mA
• Voltage - Supply, Single/dual (±): 5 V ~ 24 V, ±2.5 V ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD8065/AD8066
INPUT-TO-OUTPUT COUPLING
To minimize capacitive coupling between the inputs and output,
the output signal traces should not be parallel with the inputs.
WIDEBAND PHOTODIODE PREAMP
Figure 58 shows an I/V converter with an electrical model of a
photodiode. The basic transfer function is
where I
parallel combination of R
The stable bandwidth attainable with this preamp is a function
of R
capacitance at the amplifier’s summing junction, including C
and the amplifier input capacitance. R
produce a pole in the amplifier’s loop transmission that can
result in peaking and instability. Adding C
loop transmission that compensates for the pole’s effect and
reduces the signal bandwidth. It can be shown that the signal
bandwidth resulting in a 45° phase margin (f
where f
resistor, and C
junction (amplifier + photodiode + board parasitics).
The value of C
F
, the gain bandwidth product of the amplifier, and the total
V
C
f
( )
OUT
F
45
CR
PHOTO
=
is the amplifier crossover frequency, R
=
=
2
is the output current of the photodiode, and the
I
π
1
2
PHOTO
S
F
π
+
×
is the total capacitance at the amplifier summing
that produces f
×
sC
R
C
R
f
F
S
CR
F
×
F
×
R
R
×
F
f
CR
F
C
I
PHOTO
F
S
and C
(45)
V
B
F
sets the signal bandwidth.
can be shown to be
F
and the total capacitance
C
F
S
creates a 0 in the
(45)
) is defined by
F
is the feedback
R
Figure 58. Wideband Photodiode Preamp
SH
= 10
11
C
Ω
F
+ C
Rev. J | Page 24 of 28
S
S
The frequency response in this case shows about 2 dB of
peaking and 15% overshoot. Doubling C
bandwidth in half results in a flat frequency response with
about 5% transient overshoot.
The preamp’s output noise over frequency is shown in Figure 59.
The pole in the loop transmission translates to a 0 in the
amplifier’s noise gain, leading to an amplification of the input
voltage noise over frequency. The loop transmission 0
introduced by C
bandwidth extends past the preamp signal bandwidth and is
eventually rolled off by the decreasing loop gain of the
amplifier. Keeping the input terminal impedances matched is
recommended to eliminate common-mode noise peaking
effects, which adds to the output noise.
Integrating the square of the output voltage noise spectral
density over frequency and then taking the square root allows
users to obtain the total rms output noise of the preamp. Table 5
summarizes approximations for the amplifier and feedback and
source resistances. Noise components for an example preamp
with R
1.6 MHz) are also listed.
R
F
VEN
F
f
1
= 50 kΩ, C
R
F
Figure 59. Photodiode Voltage Noise Contributions
C
NOISE
D
C
C
NOISE DUE TO AMPLIFIER
F
M
M
limits the amplification. The noise gain
f
f
f
f
2
1
2
3
S
C
R
=
=
=
F
= 15 pF, and C
F
2πR
(C
2π R
1
S
F
C
+ C
F
F
(C
FREQUENCY (Hz)
M
F
+ 2C
VEN (C
+ C
f
CR
1
S
D
+ C
+ C
F
M
+ C
F
F
+ 2C
) /C
= 2 pF (bandwidth of about
V
S
O
F
+ C
D
)
M
F
+ 2C
and cutting the
D
)/C
F
f
3