OPA830 datasheet(32/66 Pages) TI2

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(

)

IN+

REF

1 +

+ V

OUT

ö æ

´ç

÷ ç

ø è

(3)

The signal gain of the circuit is set by

ö æ

÷ ç

ø è

G 1

G =

1 +

. VCM is rejected, and VREF provides a level

shift around which the output signal swings. The single-ended output signal is in-phase with the differential input

signal.

OPA 836

½ OPA2836

VIN-

VIN+

VSIG-

VSIG+

VCM

RG1

RF1

RG2

RF2

VOUT

G[(V

)-(

SIG+

)]

SIG-

VREF

½ OPA2836

Figure 9-1. Instrumentation Amplifier

Integrated solutions are available, but the OPA836 device provides a much lower-power, high-frequency

solution. For best CMRR performance, resistors must be matched. A good guideline to follow is CMRR ≈ the

resistor tolerance; so, 0.1% tolerance will provide approximately 60-dB CMRR.

9.1.4 Attenuators

The noninverting circuit of Figure 8-1 has minimum gain of 1. To implement attenuation, a resistor divider can be

placed in series with the positive input, and the amplifier set for gain of 1 by shorting VOUT to VIN– and removing

RG. Because the operational amplifier input is high impedance, the resistor divider sets the attenuation.

The inverting circuit of Figure 8-2 can be used as an attenuator by making RG larger than RF. The attenuation is

the resistor ratio. For example, a 10:1 attenuator can be implemented with RF = 1 kΩ and RG = 10 kΩ.

9.1.5 Single-Ended-to-Differential Amplifier

Figure 9-2 shows an amplifier circuit that is used to convert single-ended signals to differential, and provides

gain and level shifting. This circuit can be used for converting signals to differential in applications like line

drivers for Cat5 cabling or driving differential-input SAR and ΔΣ ADCs.

With VIN = VREF + VSIG , the output of the amplifier may be calculated according to Equation 4.

REF

OUT+

OUT-

= G x V

+ V

and V

= -G x V

+ V

Where: G = 1 +

(4)

The differential-signal gain of the circuit is 2 × G, and VREF provides a reference around which the output signal

swings. The differential output signal is in-phase with the single-ended input signal.

OPA836, OPA2836

SLOS712J – JANUARY 2011 – REVISED MARCH 2021

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OPA830 Datasheet(PDF) 32 Page - Texas Instruments

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