The OPA192 buffer is configured in a dual-feedback configuration to provide stability while driving the REF pin

and 22nF bypass capacitor. RISO is a 20Ω isolation resistor that provides separation of two feedback paths for

optimized stability. Feedback path number one is through feedback resistor, RF = 2kΩ, connected directly to the

REF pin. Feedback path number two is through feedback capacitor CF = 2nF connected to the output of the op

amp. The circuit provides a loop gain phase margin of 86°. The noninverting input of the OPA192 buffer has

a low-pass filter with R = 1kΩ, C = 10nF to reduce the resistive divider thermal noise. Using any other load

capacitance requires recalculation of the stability components: RF, CF, and RISO. If modifying the REF bypass

capacitance, verify the circuit is stable with simulation using the OPA192 TINA-TI model (or PSpice®-for-TI

model), and confirm the circuit provides more than 60° of phase margin.

8.2.1.3 Application Curves

Table 8-2 lists the PGA849 output voltage with different gain configurations, and Figure 8-10 shows the PGA849

output voltage with a gain of 2.

Table 8-2. PGA849 Output Voltage with Different Gain Configurations

Input (mV)

Reference (V)

A2:A0

PGA Gain (V/V)

Minimum Output (V) Maximum Output (V)

±50

2.5

000

0.125

2.494

2.506

001

0.25

2.488

2.512

010

0.5

2.475

2.525

011

1

2.450

2.550

100

2

2.400

2.600

101

4

2.300

2.700

110

8

2.100

2.900

111

16

1.700

3.300

Time

0s

0.5ms

1.0ms

1.5ms

2.0ms

2.5ms

3.0ms

V(V_OUT)

2.4V

2.5V

2.6V

V(V_INP) - V(V_INN)

-50mV

0V

50mV

Figure 8-10. PGA849 Output Voltage with a Gain of 2, Reference = 2.5V

www.ti.com

PGA849

SBOSAG3A – MARCH 2024 – REVISED DECEMBER 2024

Copyright © 2024 Texas Instruments Incorporated

Submit Document Feedback

27

Product Folder Links: PGA849