OPA2325 Datasheet, PDF (18/32 Pages) Texas Instruments – Precision, 10-MHz, Low-Noise, Low-Power, RRIO, CMOS Operational Amplifier

OPA2325
SBOS637 – OCTOBER 2016
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Application Information (continued)
8.1.3 Driving an Analog-to-Digital Converter
The low-noise and wide-gain bandwidth of the OPA2325, combined with rail-to-rail input/output and zero-
crossover distortion, make the device an ideal input driver for ADCs. Figure 45 shows the OPA2325 driving an
ADC. The amplifier is connected as a unity-gain, noninverting buffer.
3.3 V
Input
OPA2325
+
R
C
VREF
ADC
VSS
VDD
5V
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Figure 45. The OPA2325 as an Input Driver for ADCs
8.2 Typical Application
Operational amplifiers are commonly used as unity-gain buffers. Figure 46 shows the schematic for an amplifier
configured as a unity-gain buffer. If the input signal range to the amplifier is very close to the rails or includes the
rails, a rail-to-rail amplifier must be used. However, regular rail-to-rail amplifiers introduce significant distortion to
the signal. This design compares the distortion introduced by a typical CMOS input amplifier with that of the
OPA2325 (a zero-crossover amplifier).
4-VPP
Sine Wave
2.5 V
±
VOUT
+
OPA2325
-2.5 V
GND
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Figure 46. The OPA2325 Configured as a Unity-Gain Buffer Amplifier
8.2.1 Design Requirements
The following parameters are used for this design example:
• Gain = +1 V/V (inverting gain)
• V+ = 2.5 V, V– = –2.5 V
• Input signal = 4 V_PP, f = 1-kHz sine wave
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