OPA2690IDBV BURR-BROWN [Burr-Brown Corporation], OPA2690IDBV Datasheet - Page 15

• Manufacturer Part Number: OPA2690IDBV
• Description: Dual, Wideband, Voltage-Feedback OPERATIONAL AMPLIFIER with Disable
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

HIGH-PERFORMANCE DAC
TRANSIMPEDANCE AMPLIFIER
High-frequency
(DACs) require a low distortion output amplifier to retain
their SFDR performance into real-world loads. Figure 5
shows a single-ended output drive implementation. The
diagram shows the signal output current(s) connected into
the virtual ground summing junction(s) of the OPA2690,
which is set up as a transimpedance stage or I-V converter.
If the DAC requires that its outputs terminate to a
compliance voltage other than ground for operation, the
appropriate voltage level may be applied to the
noninverting input of the OPA2690. The DC gain for this
circuit is equal to R
capacitance (C
noise gain for the OPA2690 that may cause peaking in the
closed-loop frequency response. C
compensate for this noise gain peaking. To achieve a flat
transimpedance frequency response, the pole in each
feedback network should be set to:
which will give a cutoff frequency f
www.ti.com
V
DIS
2pR
f
D
*3dB
1
in Figure 5) will produce a zero in the
F
DDS
F
C
. At high frequencies, the DAC output
F
+
+
Figure 6. 2-Channel Video Multiplexer (SO-14 package only)
Digital-to-Analog
2pR
4pR
GBP
Video 1
Video 2
+5V
GBP
F
C
F
C
D
F
−3dB
D
is added across R
of approximately:
75 Ω
75Ω
340Ω
340Ω
146Ω
146Ω
Converters
2kΩ
2kΩ
(1)
(2)
F
to
O P A 2 6 9 0
O P A 2 6 9 0
+5V
−5V
+5V
−5V
1 /2
1 /2
DISB
DISA
WIDEBAND VIDEO MULTIPLEXING
One common application for video speed amplifiers that
include a disable pin is to wire multiple amplifier outputs
together, then select which one of several possible video
inputs to source onto a single line. This simple wired-OR
video multiplexer can be easily implemented using the
OP2690I-14D (SO-14 package only), as shown in
Figure 6.
402Ω
402Ω
High−Speed
Figure 5. DAC Transimpedance Amplifier
DAC
I
− I
O
O
SBOS238D − JUNE 2002 − REVISED DECEMBER 2004
C
C
50Ω
D1
D2
50 Ω
O P A 2 6 9 0
O P A 2 6 9 0
82.5Ω
82.5Ω
1/2
1/2
C
C
R
R
GBP → Gain Bandwidth
Product (Hz) for the OPA2690
75 Ω Cable
F1
F2
F1
F2
RG−59
75Ω Load
− V
V
O
O
OPA2690
= I
= − I
O
R
O
F
R
F
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