OPA2325 Datasheet, PDF (20/32 Pages) Texas Instruments – Precision, 10-MHz, Low-Noise, Low-Power, RRIO, CMOS Operational Amplifier

OPA2325
SBOS637 – OCTOBER 2016
www.ti.com
Typical Application (continued)
The N-channel pair is active for input voltages close to the positive rail, typically (V+) – 1 V to 200 mV above the
positive supply, and the P-channel pair is on for inputs from 200 mV below the negative supply to approximately
(V+) – 1 V. There is a small transition region, typically (V+) – 1.1 V to (V+) – 0.9 V, in which both pairs are on.
This transition region is shown in Figure 48 for a traditional rail-to-rail input CMOS amplifier. Within this transition
region, PSRR, CMRR, offset voltage, offset drift, and THD can be degraded when compared to device operation
outside of this region.
3
2
1
0
-1
-2 _-V
+V
-3
-0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Input Common-Mode Voltage (V)
Figure 48. Input Offset Voltage vs Common-Mode Voltage
(For Traditional Rail-to-Rail Input CMOS Amplifiers)
The OPA2325 amplifier includes an internal charge pump that powers the amplifier input stage with an internal
supply rail that is higher than the external power supply. The internal supply rail allows a single differential pair to
operate and to be linear across the entire input common-mode voltage range, as shown in Figure 49.
+VSUPPLY
Charge Pump
IS1
VIN+
PCH1
PCH2
VIN-
e-Trim^TM
-Vsupply
Figure 49. Single Differential Input Pair with a Charge Pump (Zero-Crossover)
20
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