OPA830-EP_15 Datasheet, PDF (19/36 Pages) Texas Instruments – Low-Power, Single-Supply, Wideband Operational Amplifier

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Typical Applications (continued)
50Ω Source
V_IN
348Ω
50Ω
+5V
0.1µF
6.8µF
+
OPA830
V_O
150Ω
OPA830-EP
SBOS655 – MARCH 2014
0.01µF
R_F
750Ω
R_G
750Ω
6.8µF
+
0.1µF
−5V
Figure 52. DC-Coupled, G = +2, Bipolar Supply Specification and Test Circuit
8.2.1.1 Single-Supply ADC Interface
The ADC interface on the front page shows a DC-coupled, single-supply ADC driver circuit. Its large input and
output voltage ranges and low distortion support converters such as the THS1040 shown in the figure on page 1.
The input level-shifting circuitry was designed so that VIN can be between 0V and 0.5V, while delivering an
output voltage of 1V to 2V for the THS1040.
8.2.1.2 DC Level-Shifting
Figure 53 shows a DC-coupled non-inverting amplifier that level-shifts the input up to accommodate the desired
output voltage range. Given the desired signal gain (G), and the amount V_OUT needs to be shifted up (ΔV_OUT)
when V_IN is at the center of its range, the following equations give the resistor values that produce the desired
performance. Assume that R₄ is between 200Ω and 1.5kΩ.
NG = G + V_OUT/V_S
(1)
R₁ = R₄/G
(2)
R₂ = R₄/(NG − G)
(3)
R₃ = R₄/(NG −1)
(4)
Where:
NG = 1 + R₄/R₃
(5)
V_OUT = (G)V_IN + (NG − G)V_S
(6)
Make sure that V_IN and V_OUT stay within the specified input and output voltage ranges.
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