THS3217 Datasheet, PDF (44/73 Pages) Texas Instruments – THS3217 DC to 800-MHz, Differential-to-Single-Ended, DAC Output Amplifier

THS3217
SBOS766B – FEBRUARY 2016 – REVISED FEBRUARY 2016
www.ti.com
9.3.3.3 Switch Feedthrough to the OPS
The OPS has two logic control pins, giving four combinations of states; therefore, various feedthrough effects
must be considered. Figure 57 and Figure 58 show the feedthrough of the switches with the OPS disabled. With
the OPS enabled, the signal feedthrough from the deselected input to the OPS output is shown in Figure 87 and
Figure 88 at different closed-loop OPS gains. The results are shown for a 100-mV_PP signal at the deselected
input and are not normalized to the gain of the OPS. Adding a low-pass filter between the DAC and the D2S
inputs helps reduce the feedthrough at higher frequencies.
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
1M
OPS Gain = 2.5 V/V
OPS Gain =10 V/V
10M
100M
Frequency (Hz)
PATHSEL < 0.7 V,
100-mV_PP signal to VIN (pin 9)
1G
D506
Figure 87. Forward Feedthrough With OPS Enabled,
Internal Path Selected
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
1M
OPS Gain = 2.5 V/V
OPS Gain =10 V/V
10M
100M
Frequency (Hz)
PATHSEL > 1.3 V,
1G
D507
100-mV_PP signal to VREF (pin 14) with D2S inputs grounded
Figure 88. Forward Feedthrough With OPS Enabled,
External Path Selected
44
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