OPA835IDBVT datasheet(30/63 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

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 835

½OPA2835

VIN-

VIN+

VSIG-

VSIG+

VCM

RG1

RF1

RG2

RF2

VOUT

G[(V

)-(

SIG+

)]

SIG-

VREF

½OPA2835

Figure 9-1. Instrumentation Amplifier

Integrated solutions are available, but the OPA835 device provides a much lower-power, high-frequency

solution. For best CMRR performance, resistors must be matched. A good rule of thumb is CMRR ≈ the resistor

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

9.1.4 Attenuators

The noninverting circuit shown in Figure 8-1 has a minimum gain of 1. To implement attenuation, a resistor

divider can be placed in series with the positive input, and the amplifier set for a gain of 1 by shorting VOUT to

VIN– and removing RG. Because the op amp input is high impedance, the resistor divider sets the attenuation.

The inverting circuit of Figure 8-2 is 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 = 2 kΩ and RG = 20 kΩ.

9.1.5 Single-Ended to Differential Amplifier

Figure 9-2 shows an amplifier circuit that converts single-ended signals to differential signals and provides gain

and level shifting. This circuit can convert signals to differential in applications such as driving Cat5 cabling or

driving differential-input SAR and ΔΣ ADCs.

By setting VIN = VREF + VSIG, then 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.

OPA835, OPA2835

SLOS713J – JANUARY 2011 – REVISED MARCH 2021

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OPA835IDBVT Datasheet(PDF) 30 Page - Texas Instruments

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