LPV542 Datasheet, PDF (14/29 Pages) Texas Instruments – LPV542 Dual Nanopower 1.8 V, 490nA, RRIO CMOS Operational Amplifier

LPV542
SNOSCX9 – MARCH 2015
7 Detailed Description
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7.1 Overview
The LPV542 dual op amplifier is unity-gain stable and can operate on a single supply, making it highly versatile
and easy to use.
The LPV542 is fully specified and tested from 1.6 V to 5.5 V. Parameters that vary significantly with operating
voltages or temperature are shown in the Typical Characteristics curves.
7.2 Functional Block Diagram
7.3 Feature Description
The amplifier's differential inputs consist of a non-inverting input (+IN) and an inverting input (–IN). The amplifer
amplifies only the difference in voltage between the two inputs, which is called the differential input voltage. The
output voltage of the op-amp V_OUT is given by Equation 1:
V_OUT = A_OL (IN⁺ – IN^–)
where
• A_OL is the open-loop gain of the amplifier, typically around 100 dB (100,000x, or 100,000 Volts per microvolt).
(1)
7.4 Device Functional Modes
7.4.1 Rail-To-Rail Input
The input common-mode voltage range of the LPV542 extends to the supply rails. This is achieved with a
complementary input stage — an N-channel input differential pair in parallel with a P-channel differential pair.
The N-channel pair is active for input voltages close to the positive rail, typically (V+) – 800 mV to 200 mV above
the positive supply, while the P-channel pair is on for inputs from 300 mV below the negative supply to
approximately (V+) – 800 mV. There is a small transition region, typically (V+) – 1.2 V to (V+) – 0.8 V, in which
both pairs are on. This 400 mV transition region can vary 200 mV with process variation. Within the 400 mV
transition region PSRR, CMRR, offset voltage, offset drift, and THD may be degraded compared to operation
outside this region.
7.4.2 Supply Current Changes over Common Mode
Because of the ultra-low supply current, changes in common mode voltages will cause a noticeable change in
the supply current as the input stages transition through the transition region, as shown in Figure 37 below.
1000
900
800
700
600
500
400
300
125°C
85°C
200
25°C
100
0°C
-40°C
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Common Mode Voltage (V)
C001
Figure 37. Supply Current Change over Common Mode at 5 V
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