OPA607 datasheet(26/50 Pages) TI1

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REF

VIN

VREF

VSIG

VREF

-(RF/RG)VSIG

VS+

VS-

VIN

VREF

VSIG

VREF

(1+RF/RG)VSIG

VS+

VS-

OPA810

SBOS799A – AUGUST 2019 – REVISED DECEMBER 2019

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Application Information (continued)

9.1.2 Selection of Feedback Resistors

The OPA810 is a classic voltage feedback amplifier with each channel having two high-impedance inputs and a

low-impedance output. Standard application circuits (as shown in Figure 64 and Figure 65) include the

noninverting and inverting gain configurations. The DC operating point for each configuration is level-shifted by

the reference voltage VREF which is typically set to midsupply in single-supply operation. VREF is often connected

to ground in split-supply applications.

Figure 64. Noninverting Amplifier

Figure 65. Inverting Amplifier

The closed-loop gain of an amplifier in noninverting configuration is shown in Equation 1.

(3)

The closed-loop gain of an amplifier in an inverting configuration is shown in Equation 2.

(4)

The magnitude of the low-frequency gain is determined by the ratio of the magnitudes of the feedback resistor

(RF) and the gain setting resistor RG. The order of magnitudes of the individual values of RF and RG offer a trade-

off between amplifier stability, power dissipated in the feedback resistor network, and total output noise. The

feedback network increases the loading on the amplifier output. Using large values of the feedback resistors

reduces the power dissipated at the amplifier output. On the other hand, this increases the inherent voltage and

amplifier current noise contribution seen at the output while lowering the frequency at which a pole occurs in the

feedback factor (β). This pole causes a decrease in the phase margin at zero-gain crossover frequency and

potential instability. Using small feedback resistors increases power dissipation and also degrades amplifier

linearity due to a heavier amplifier output load. Figure 66 illustrates a representative schematic of the OPA810 in

an inverting configuration with the input capacitors shown.

OPA607 Datasheet(PDF) 26 Page - Texas Instruments

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