ad797bn Analog Devices, Inc., ad797bn Datasheet - Page 18

• Manufacturer Part Number: ad797bn
• Description: Ultralow Distortion, Ultralow Noise Op Amp
• Manufacturer: Analog Devices, Inc.

AD797
Amorphous (Photodiode) Detector
Large area photodiodes (C
detectors (amorphous Si) have optimum performance when
used in conjunction with amplifiers with very low voltage rather
than very low current noise.
with an amorphous Si (C
adjusted for flatness using capacitor C
dominated by voltage noise amplified by the ac noise gain. The
AD797’s excellent input noise performance gives 27 μV rms
total noise in a 1 MHz bandwidth, as shown by Figure 48.
–30
–40
–50
–60
–70
–80
100
**Use Power Supply Bypassing Shown in Figure 35
Figure 52. Total Integrated Voltage Noise and V
I
S
1k
Figure 51. Amorphous Detector Preamp
of Amorphous Detector Preamp
C
1000pF
S
10k
S
FREQUENCY (Hz)
V
= 1000 pF) detector. The response is
OUT
S
≥ 500 pF) and certain image
Figure 51 shows the AD797 used
2
3
100k
100Ω
AD797
10kΩ
+V
–V
7
4
S
L
S
50pF
, while the noise is
1M
C
L
**
**
6
NOISE
10M
OUT
100M
100
0
80
60
20
40
Rev. E | Page 18 of 20
Professional Audio Signal Processing—DAC Buffers
The low noise and low distortion of the AD797 make it an ideal
choice for professional audio signal processing. An ideal I-to-V
converter for a current output DAC would simply be a resistor
to ground, were it not for the fact that most DACs do not
operate linearly with voltage on their output. Standard practice
is to operate an op amp as an I-to-V converter creating a virtual
ground at its inverting input. Normally, clock energy and
current steps must be absorbed by the op amp’s output stage.
However, in the configuration of
high frequency energy to ground, while correctly reproducing
the desired output with extremely low THD and IMD.
**Use Power Supply Bypassing Shown in Figure 35
AD1862
DAC
Figure 53. A Professional Audio DAC Buffer
Figure 54. Offset Null Configuration
2000pF
C1
2
3
–V
4
AD797
S
1
2
3
+V
82pF
7
C
S
20kΩ
F
5
Figure 53, Capacitor C
AD797
3kΩ
+V
–V
6
V
7
4
S
S
OS
ADJUST
100Ω
**
**
6
F
shunts