OPA2325 Datasheet, PDF (21/32 Pages) Texas Instruments – Precision, 10-MHz, Low-Noise, Low-Power, RRIO, CMOS Operational Amplifier

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OPA2325
SBOS637 – OCTOBER 2016
Typical Application (continued)
The unique zero-crossover topology shown in Figure 49 eliminates the input offset transition region, typical of
most rail-to-rail input operational amplifiers. This topology allows the OPA2325 to provide superior CMRR across
the entire common-mode input range that extends 100 mV beyond both power-supply rails. Figure 50 shows the
input offset voltage versus input common-mode voltage plot for the OPA2325.
150
125
100
75
50
25
0
±25
±50
±75
±100
±125
V_CM = ±2.85 V
V_CM = 2.85 V
±150
±3
±2
±1
0
1
2
3
V_CM (V)
C003
Figure 50. Offset Voltage vs Common-Mode Voltage (OPA2325, Zero-Crossover Amplifier)
The OPA2325 and a typical CMOS amplifier were used in identical circuits where these amplifiers were
configured as a unity-gain buffer amplifier; see Figure 51 and Figure 52. A pure sine wave with an amplitude of
2 V (4 V_PP) was given as input to the two identical circuits of Figure 51 and Figure 52. The outputs of these
circuits were captured on a spectrum analyzer. Figure 53 and Figure 54 illustrate the output voltage spectrum for
the OPA2325 and a typical CMOS rail-to-rail amplifier, respectively. The output of the OPA2325 has very few
spurs and harmonics when compared to the typical rail-to-rail CMOS amplifier, as illustrated in Figure 55.
4-VPP
Sine Wave
2.5 V
±
VOUT
+
OPA2325
-2.5 V
GND
Copyright © 2016, Texas Instruments Incorporated
Figure 51. OPA2325 as a Unity-Gain Buffer
4-VPP
Sine Wave
2.5 V
±
VOUT
+
Typical CMOS
-2.5 V _{rail-to-rail amplifiers}
GND
Figure 52. Typical CMOS Rail-to-Rail Amplifier as a Unity-
Gain Buffer
Copyright © 2016, Texas Instruments Incorporated
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