THS3217 Datasheet, PDF (49/73 Pages) Texas Instruments – THS3217 DC to 800-MHz, Differential-to-Single-Ended, DAC Output Amplifier

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THS3217
SBOS766B – FEBRUARY 2016 – REVISED FEBRUARY 2016
Device Functional Modes (continued)
9.4.1.3 External Connection
In the configuration shown in Figure 92, the bias to PATHSEL (pin 4) is changed in order to select the external
input of the OPS. The external D2S output drives a low insertion loss, third-order Bessel filter. The filter in this
example is designed with a low frequency insertion loss of 1.2 dB and f_–3dB = 140 MHz, and results in an
additional insertion loss of 1 dB at 100 MHz. The OPS gain is slightly increased to recover the filter loss, in order
to give an input to output gain of 5 V/V. Using an interstage filter between the D2S and the OPS improves the
step response by reducing the overshoot.
49.9
Differential
V_IN
49.9
VPATHSEL > 1.3 V
16
15
1
50 k
2 x1
50 k
x1
50
+
250
500
3 x1
14
100
13
18.5 k
130
12
249
49.9
11
AV= 5 V/V
To
50-Ÿ /RDG
10
18.5 k
4
5
6
34
1-dB loss
at 100 MHz
9
249
7
8
Low Insertion Loss
3rd-Order Bessel Filter
33 nH
10 pF
52 pF
Figure 92. External Path Configuration With Interstage Low-Pass Filter
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