AD8608 Analog Devices, AD8608 Datasheet - Page 19

• Manufacturer Part Number: AD8608
• Description: Precision, Low Noise, CMOS, Rail-to-Rail, Input/Output Operational Amplifier (Quad)
• Manufacturer: Analog Devices

Specifications of AD8608

• Vcc-vee: 2.7V to 6V
• Isy Per Amplifier: 1.2mA
• Packages: SOIC,SOP
• -3db Bandwidth: 10MHz
• Slew Rate: 5V/µs
• Vos: 20µV
• Ib: 200fA
• # Opamps Per Pkg: 4
• Input Noise (nv/rthz): 6.5nV/rtHz

Data Sheet
I-V CONVERSION APPLICATIONS
PHOTODIODE PREAMPLIFIER APPLICATIONS
The low offset voltage and input current of the
it an excellent choice for photodiode applications. In addition,
the low voltage and current noise make the amplifier ideal for
application circuits with high sensitivity.
The input bias current of the amplifier contributes an error
term that is proportional to the value of R
The offset voltage causes a dark current induced by the shunt
resistance of the Diode R
the output of the amplifier. The error voltage is written as
Typically, R
E
R
O
D
PHOTODIODE
=
Figure 52. Equivalent Circuit for Photodiode Preamp
V
F
OS
is smaller than R
I
D




1
+
R
50pF
R
C
D
F
D




+
D
. These error terms are combined at
R
F
I
D
B
, thus R
V
OS
F
/R
V1
500mV
V2
500mV
AD8605
1µF
C1
1µF
D
C2
F
10MΩ
.
10pF
can be ignored.
R
C
F
F
Figure 53. Single-Supply Headphone/Speaker Amplifier
20kΩ
20kΩ
AD8605
20kΩ
20kΩ
R1
R2
R7
R8
make
V
OUT
Rev. L | Page 19 of 24
3
2
5
6
1/2
AD8606
1/2
AD8606
8
4
8
4
5V
5V
At room temperature, the
0.2 pA and an offset voltage of 100 µV. Typical values of R
in the range of 1 GΩ.
For the circuit shown in Figure 52, the output error voltage is
approximately 100 µV at room temperature, increasing to about
1 mV at 85°C.
The maximum achievable signal bandwidth is
where f
AUDIO AND PDA APPLICATIONS
The low distortion and wide dynamic range of the AD860x
make it a great choice for audio and PDA applications,
including microphone amplification and line output buffering.
Figure 53 shows a typical application circuit for headphone/
line-out amplification.
R1 and R2 are used to bias the input voltage at half the supply,
which maximizes the signal bandwidth range. C1 and C2 are
used to ac couple the input signal. C1, R1, and R2 form a high-
pass filter whose corner frequency is 1/[2π(R1||R2)C1].
The high output current of the
resistive loads.
The circuit in Figure 53 is tested to drive a 16 Ω headphone. The
THD + N is maintained at approximately −60 dB throughout the
audio range.
1
7
f
MAX
100µF
100µF
t
C4
is the unity gain frequency of the amplifier.
C3
=
R3
1kΩ
R5
1kΩ
20Ω
2
20Ω
R6
R4
π
HEADPHONES
R
f
F
t
C
F
AD8605/AD8606/AD8608
AD8605
AD8606
has an input bias current of
allows it to drive heavy
D
are