THS4551 Datasheet, PDF (51/70 Pages) Texas Instruments – Low-Noise, Precision, 150-MHz, Fully Differential Amplifier

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THS4551
SBOS778A – APRIL 2016 – REVISED AUGUST 2016
10.2.2.3 Application Curves
The bandwidth is controlled to 88 kHz by using the 2.4-nF feedback capacitors. Amplifier stability is controlled by
the 20-nF differential capacitor across the DAC outputs. The added 4.4 Ω in series with the feedback 2.2-nF
capacitor isolates this capacitance from the inductive open-loop output impedance. Include the DAC source
capacitance in any final design analysis. Running the frequency response for this circuit provides this result. The
63.5-dBΩ gain is the 1.5-kΩ transimpedance gain provided in this design.
70
240
Gain (dB)
65
Phase (deg) ²⁰⁰
60
160
55
120
50
80
45
40
40
0
35
-40
30
-80
25
-120
20
1k
10k
100k
1M
Frequency (Hz)
10M
-160
100M
D074
Figure 91. Gain and Phase Plot of DAC Output Driver
Running a full-scale sine wave at 1 kHz with ±1.95 mA on each output from the DAC at 180° out of phase, and
probing each THS4551 output pin separately results in the expected ±1.46 V on each output pin, as shown in
Figure 92. More output swing is available for the RRO device using the ±2.5-V supplies provided by the
LM27762 by simply increasing the feedback resistor values.
2.5
2
V_OUT-
V_OUT+
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Time (ms)
D075
Figure 92. Output Waveform of the DAC Output Driver
Although this example is on the audio signal generation side, the THS4551 can also be used to convert a single-
ended line input to a differential driver into an audio ADC.
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