OPA835 datasheet(10/21 Pages) TI1

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½ O PA283 4

Sign al and bias to

next sta ge

2.5 V

GVSIG

2.5 V

VSIG

5 V

VOUT

Sign al and bias from

previou s stag e

2.5 V

REF

5 V

Load

VOUT

5 V

½ OPA2834

VSIG

2.5 V

OPA2834

SBOS973 – JUNE 2019

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Device Functional Modes (continued)

8.4.2 Single-Supply Operation (2.7 V to 5.4 V)

Often, newer systems use a single power supply to improve efficiency and reduce the cost of the power supply.

The OPA2834 is designed for use with single-supply power operation and can be used with single-supply power

with no change in performance from split supply, as long as the input and output are biased within the linear

operation of the device.

To change the circuit from split-supply to single-supply, level shift all voltages by half the difference between the

power-supply rails. For example, Figure 7 shows changing from a ±2.5-V split supply to a 5-V single-supply.

Figure 7. Single-Supply Concept

A practical circuit has an amplifier or some other circuit providing the bias voltage for the input, and the output of

this amplifier stage provides the bias for the next stage.

Figure 8 shows a typical noninverting amplifier circuit. With a 5-V single-supply, a mid-supply reference generator

is needed to bias the negative side through RG. To cancel the voltage offset that is otherwise caused by the input

bias currents, R1 is selected to be equal to RF in parallel with RG. For example, if a gain of 2 is required and RF =

3.6 kΩ, select RG = 3.6 kΩ to set the gain, and R1 = 1.8 kΩ for bias current cancellation. The value for C is

dependent on the reference, and TI recommends a value of at least 0.1 µF to limit noise.

Figure 8. Noninverting Single Supply With Reference

Figure 9 illustrates a similar noninverting single-supply scenario with the reference generator replaced by the

Thevenin equivalent using resistors and the positive supply. RG’ and RG” form a resistor divider from the 5-V

supply and are used to bias the negative side with the parallel sum equal to the equivalent RG to set the gain. To

cancel the voltage offset that is otherwise caused by the input bias currents, R1 is selected to be equal to RF in

parallel with RG’ in parallel with RG” (R1= RF || RG’ || RG”). For example, if a gain of 2 is required and RF = 3.6 kΩ,

selecting RG’ = RG” = 7.2 kΩ gives an equivalent parallel sum of 3.6 kΩ, sets the gain to 2, and references the

input to mid supply (2.5 V). R1 is set to 1.8 kΩ for bias current cancellation. The resistor divider costs less than

the 2.5-V reference in Figure 9 but can increase the current from the 5-V supply.

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