8.1.2 Achieving an Output Level of Zero Volts

Certain single-supply applications require the op

‑amp output to swing from 0 V to a positive full-scale voltage

and have high accuracy. An example is an op amp employed to drive a single-supply ADC having an input range

from 0 V to 3.3 V. Rail-to-rail output amplifiers with very light output loading can achieve an output level within

few millivolts of 0 V (or V+ at the high end), but not true 0 V. Furthermore, the deviation from 0 V only becomes

greater as the required load current increases. This increased deviation is a result of limitations of the CMOS

output stage.

When a pulldown resistor is connected from the amplifier output to a negative voltage source, the TLVx365

can achieve an output level of 0 V, and even a few millivolts below 0 V. Figure 8-3 shows a circuit using this

technique.

V

OUT

RP =10 kΩ

500 µA

TLV365

V

IN

V+ = +5 V

Op Amps

Negative

Supply

Grounded

−V = −5 V

(Additional

Negative Supply)

Figure 8-3. Swing-to-Ground

A pulldown current of approximately 500 μA is required when TLVx365 is connected as a unity-gain buffer.

Pulldown resistor RL is calculated from RL = [(VO − VNEG) / (500 μA)].

Figure 8-4 shows the offset voltage vs output swing.

Output Voltage (V)

-3 -2.5 -2 -1.5 -1 -0.5

0

0.5

1

1.5

2

2.5

3

−20m

−15m

−10m

−5m

0

5m

10m

15m

20m

VS = ±2.75 V

Figure 8-4. Offset Voltage vs Output Swing

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TLV365, TLV2365

SBOSAA8C – DECEMBER 2022 – REVISED AUGUST 2024

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