OPA830 datasheet(29/66 Pages) TI2

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OPA 836

Signal and bias to

next stage

Signal and bias

from previous stage

VSIG

2.5 V

5 V

2.5 V

VOUT

GVSIG

5 V

2.5 V

REF

Figure 8-8. Noninverting Single Supply With Reference

Figure 8-9 shows 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 their parallel sum equal to the equivalent RG to set the gain.

To cancel the voltage offset that would otherwise be 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 gain of 2 is required and RF

= 1 kΩ, selecting RG’ = RG” = 2 kΩ gives equivalent parallel sum of 1 kΩ, sets the gain to 2, and references the

input to mid supply (2.5 V). R1 is then set to 499 Ω for bias-current cancellation. The resistor divider costs less

than the 2.5 V reference in Figure 8-8 but may increase the current from the 5-V supply.

OPA 836

Signal and bias to

next stage

Signal and bias

from previous stage

2.5 V

5 V

R ’

R ”

VOUT

GVSIG

5 V

VSIG

Figure 8-9. Noninverting Single Supply With Resistors

Figure 8-10 shows a typical inverting amplifier situation. With 5-V single supply, a mid-supply reference

generator is needed to bias the positive side through R1. To cancel the voltage offset that would otherwise

be caused by the input bias currents, R1 is selected to be equal to RF in parallel with RG. For example if gain of

–2 is required and RF = 1 kΩ, select RG = 499 Ω to set the gain and R1 = 332 Ω for bias-current cancellation.

The value for C is dependent on the reference, but TI recommends a value of at least 0.1 µF to limit noise into

the operational amplifier.

www.ti.com

OPA836, OPA2836

SLOS712J – JANUARY 2011 – REVISED MARCH 2021

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OPA830 Datasheet(PDF) 29 Page - Texas Instruments

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