THS10082_09 Datasheet, PDF (33/37 Pages) Texas Instruments – 10-BIT, TWO ANALOG INPUT, 8-MSPS, SIMULTANAEOUS SAMPLING

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THS10082
SLAS254B − MAY 2002 − REVISED NOVEMBER 2002
DC COUPLING
An operational amplifier can be configured to shift the signal level according to the analog input voltage range of the
THS10082. The analog input voltage range of the THS10082 goes from 1.5 V to 3.5 V. An op-amp specified for 5-V single
supply can be used as shown in Figure 42.
Figure 42 shows an application example where the analog input signal in the range from −1 V up to 1 V is shifted by an
op-amp to the analog input range of the THS10082 (1.5 V to 3.5 V). The op-amp is configured as an inverting amplifier with
a gain of −1. The required dc voltage of 1.25 V at the noninverting input is derived from the 2.5-V output reference REFOUT
of the THS10082 by using a resistor divider. Therefore, the op-amp output voltage is centered at 2.5 V. The use of ratio
matched, thin-film resistor networks minimizes gain and offset errors.
1V
0V
−1 V
R
1.25 V
R
5V
_
+
3.5 V
2.5 V
1.5 V
RS
THS10082
AINP
REFIN
REFOUT
R
R
Figure 42. Level-Shift for DC-Coupled Input
DIFFERENTIAL MODE OF OPERATION
For the differential mode of operation, a conversion from single-ended to differential is required. A conversion to differential
signals can be achieved by using an RF-transformer, which provides a center tap. Best performance is achieved in
differential mode.
Mini Circuits
T4−1
49.9 Ω
R
200 Ω ^C
R
C
THS10082
AINP
AINM
REFOUT
Figure 43. Transformer Coupled Input
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