THS4150CDGN Datasheet, PDF (14/34 Pages) Texas Instruments – HIGH-SPEED DIFFERENTIAL I/O AMPLIFIERS

THS4150
THS4151
SLOS321G – MAY 2000 – REVISED MARCH 2009........................................................................................................................................................... www.ti.com
DATA CONVERTERS
Data converters are one of the most popular applications for the fully differential amplifiers. The following
schematic shows a typical configuration of a fully differential amplifier attached to a differential ADC.
0.1 µF
V_CC
5V
V_IN
+-
V_OCM
-+
-5 V
V_CC-
V_DD
AV_DD DV_DD
A_IN1
A_{IN2 AVSS}
V_ref
Figure 31. Fully Differential Amplifier Attached to a Differential ADC
Fully differential amplifiers can operate with a single supply. V_OCM defaults to the midrail voltage, V_CC/2. The
differential output may be fed into a data converter. This method eliminates the use of a transformer in the circuit.
If the ADC has a reference voltage output (V_ref), then it is recommended to connect it directly to the V_OCM of the
amplifier using a bypass capacitor for stability. For proper operation, the input common-mode voltage to the input
terminal of the amplifier should not exceed the common-mode input voltage range.
0.1 µF
V_CC
5V
V_IN
+-
V_OCM
-+
V_DD
AV_DD DV_DD
A_IN1
A_{IN2 AVSS}
V_ref
Figure 32. Fully Differential Amplifier Using a Single-Supply
Some single-supply applications may require the input voltage to exceed the common-mode input voltage range.
In such cases, the following circuit configuration is suggested to bring the common-mode input voltage within the
specifications of the amplifier.
0.1 µF
V_CC
R_f V_CC
R_PU
R_(g)
5V
V_IN
+
V_{P VOCM}
-
R_(g)
R_PU
V_CC
-+
R_f
V_DD
V_OUT
AV_DD
A_IN1
DV_DD
THS1206
V_OUT ^{AIN2 AVSS}
V_ref
Figure 33. Circuit With Improved Common-Mode Input Voltage
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