SLPS785 Data sheet

SLPS785 December 2023 RES11A

PRODUCTION DATA

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)

DDF|8

Thermal pad, mechanical data (Package|Pins)

Orderable Information

8.1.2.1 Instrumentation Amplifier Common-Mode Rejection Analysis

The differential-input, differential-output instrumentation amplifier shown in Figure 8-3 has a common-mode gain of A_CM = 1 V/V. The differential gain is described by the following (assuming an ideal amplifier):

Equation 24.

A_{D} = \frac{R_{G1} + R_{G2}}{R_{IN1} + R_{IN2}} + 1 = G_{nom} \times \frac{(1± t_{RG1}) + (1± t_{RG2})}{(1± t_{RIN1}) + (1± t_{RIN2})} + 1

Because the worst-case-stage CMRR occurs when the differential gain is lowest, and the common-mode gain is unity, the minimum CMRR is evaluated as:

Equation 25.

\frac{A_{D}}{A_{CM}} = G_{nom} \times \frac{(1– t_{RG1}) + (1– t_{RG2})}{(1+ t_{RIN1}) + (1+ t_{RIN2})} + 1 = G_{nom} \times \frac{1.9995}{2.0005} + 1

For example, for an instrumentation amplifier with RES11A90, the worst-case CMRR is:

Equation 26.

\frac{A_{D}}{A_{CM}} = G_{nom} \times \frac{(1– t_{RG1}) + (1– t_{RG2})}{(1+ t_{RIN1}) + (1+ t_{RIN2})} + 1 = 9 V/V \times \frac{1.9995}{2.0005} + 1 = 9.9955 V/V