OPA2191 datasheet(23/59 Pages) TI

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8.3 Feature Description

8.3.1 Input Protection Circuitry

The OPAx191 uses a unique input architecture to eliminate the need for input protection diodes but still provides

robust input protection under transient conditions. Conventional input diode protection schemes shown in Figure

8-1 can be activated by fast transient step responses and can introduce signal distortion and settling time

delays because of alternate current paths, as shown in Figure 8-2. For low-gain circuits, these fast-ramping input

signals forward-bias back-to-back diodes that cause an increase in input current, resulting in extended settling

time.

OPAx191

36 V

~0.7 V

VOUT

V+

Conventional Input Protection

Limits Differential Input Range

OPAx191 Provides Full 36-

V Differential Input Range

VIN+

VIN

VOUT

V+

VIN+

VIN

Figure 8-1. OPA191 Input Protection Does Not Limit Differential Input Capability

Input Low-Pass Filter

Ron_mux

Sn+1

Simplified Mux Model

RFILT

CFILT

Vn = 10 V

Vn+1 = ±10 V

10 V

±10 V

Buffer Amplifier

Idiode_transient

10 V

~±9.3 V

VIN+

VIN±

~0.7 V

VOUT

±10 V

Ron_mux

Figure 8-2. Back-to-Back Diodes Create Settling Issues

The OPAx191 family of operational amplifiers provides a true high-impedance differential input capability

for high-voltage applications. This patented input protection architecture does not introduce additional signal

distortion or delayed settling time, making the device an optimal op amp for multichannel, high-switched, input

applications. The OPAx191 tolerates a maximum differential swing (voltage between inverting and noninverting

pins of the op amp) of up to 36 V, making the device an excellent choice for use as a comparator or in

applications with fast-ramping input signals such as multiplexed data-acquisition systems (see Figure 9-4).

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OPA191, OPA2191, OPA4191

SBOS701D – DECEMBER 2015 – REVISED AUGUST 2021

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