TLV9041UIDBVR datasheet(21/78 Pages) TI2

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VCM (V)

-3

-2.5

-2

-1.5

-1

-0.5

0.5

1.5

2.5

-2000

-1600

-1200

-800

-400

400

800

1200

1600

2000

D07_

V+ = 2.75 V, V– = –2.75 V

Figure 8-1. TLV904x Offset Voltage vs Common-

Mode

Common-Mode Voltage (V)

-4

-3

-2

-1

-2000

-1500

-1000

-500

500

1000

1500

2000

D004

V+ = 2.75 V, V– = –2.75 V

Figure 8-2. TLV900x Offset Voltage vs Common-

Mode

8.3.3 Rail-to-Rail Output

Designed as a micro-power, low-noise operational amplifier, the TLV904x delivers a robust output drive

capability. A class AB output stage with common-source transistors is used to achieve full rail-to-rail output

swing capability. For resistive loads up to 5 kΩ, the output typically swings to within 20 mV of either supply rail

regardless of the power-supply voltage applied. Different load conditions change the ability of the amplifier to

swing close to the rails.

8.3.4 Common-Mode Rejection Ratio (CMRR)

The CMRR for the TLV904x is specified in several ways so the best match for a given application can be used;

see the Electrical Characteristics table. First, the CMRR of the device in the common-mode range below the

transition region [VCM < (V+) – 0.7 V] is given. This specification is the best indicator of the capability of the

device when the application requires using one of the differential input pairs. Second, the CMRR over the entire

common-mode range is specified at (VCM = 0 V to 5.5 V). This last value includes the variations measured

through the transition region.

8.3.5 Capacitive Load and Stability

The TLV904x is designed to be used in applications where driving a capacitive load is required. As with all

operational amplifiers, there may be specific instances where the TLV904x can become unstable. The particular

operational amplifier circuit configuration, layout, gain, and output loading are some of the factors to consider

when establishing whether or not an amplifier is stable in operation. An operational amplifier in the unity-gain

(1 V/V) buffer configuration that drives a capacitive load exhibits a greater tendency to be unstable than an

amplifier operated at a higher noise gain. The capacitive load, in conjunction with the operational amplifier output

resistance, creates a pole within the feedback loop that degrades the phase margin. The degradation of the

phase margin increases when capacitive loading increases. When operating in the unity-gain configuration, the

TLV904x remains stable with a pure capacitive load up to approximately 100 pF with a good phase margin of 45°

typical. The equivalent series resistance (ESR) of some very large capacitors (CL greater than 1 μF) is sufficient

to alter the phase characteristics in the feedback loop such that the amplifier remains stable. Increasing the

amplifier closed-loop gain allows the amplifier to drive increasingly larger capacitance. This increased capability

is evident when measuring the overshoot response of the amplifier at higher voltage gains.

One technique for increasing the capacitive load drive capability of the amplifier operating in a unity-gain

configuration is to insert a small resistor (typically 10 Ω to 20 Ω) in series with the output, as shown in Figure 8-3.

This resistor significantly reduces the overshoot and ringing associated with large capacitive loads. One possible

problem with this technique, however, is that a voltage divider is created with the added series resistor and any

resistor connected in parallel with the capacitive load. The voltage divider introduces a gain error at the output

that reduces the output swing.

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SBOS836G – MARCH 2020 – REVISED MARCH 2022

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