THS3215 Datasheet, PDF (26/71 Pages) Texas Instruments – THS3215 650-MHz, Differential to Single-Ended DAC Output Amplifier

THS3215
SBOS780A – MARCH 2016 – REVISED APRIL 2016
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8.7 Feedthrough Measurement
In order to test the forward-feedthrough performance of the OPS in the disabled state, the circuit shown in
Figure 73 was used. The PATHSEL pin was driven low to select the internal path between the D2S and OPS. A
100-mV_PP, swept-frequency, sinusoidal signal was applied at the VREF pin, and the output signal was measured
at the OPS output pin (VOUT, pin 11). The transfer function from VREF to the output of the D2S at VO1 has a
gain of 0 dB, as shown in Figure 23. The results shown in Figure 57 account for the 6-dB loss due to the doubly-
terminated OPS output, and report the forward feedthrough between VOUT and VO1 at different OPS gains. The
D2S inputs were grounded through 50-Ω resistors for this test.
Network
Analyzer
GND Port 1
50
Port 2
50
49.9
49.9
16
15
1
50 k
2 x1
50 k
x1
50
+
250
500
3 x1
VREF
14
100
75
13
18.5 k
18.5 k
RG
12
11
VOUT
RF
49.9
DISABLE = High
10
PATHSEL = Low
4
9
49.9
5
6
7
8
200
Figure 73. Forward-Feedthrough Test Circuit
26
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