OPA607 datasheet(33/50 Pages) TI1

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Time (10 ns/div)

-5

-2.5

2.5

7.5

BD_M

VIN

VIN,Diff

MUX

ADC

OPA810

MUX

ADC

OPA810

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SBOS799A – AUGUST 2019 – REVISED DECEMBER 2019

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9.2.3

Multichannel Sensor Interface

High-Z input amplifiers are particularly useful when interfaced with sensors that have relatively high output

impedance. Such multichannel systems usually interface these sensors with the signal chain through a

multiplexer. Figure 77 shows one such implementation using an amplifier for the interface with each sensor, and

driving into an ADC through a multiplexer. An alternate circuit, shown in Figure 78, can use a single higher

GBWP and fast-settling amplifier at the output of the multiplexer. This architecture gives rise to large signal

transients when switching between channels, where the settling performance of the amplifier and maximum

allowed differential input voltage limits signal chain performance and amplifier reliability, respectively.

Figure 77. Multichannel Sensor Interface Using Multiple Amplifiers

Figure 78. Multichannel Sensor Interface Using a Single Higher GBWP Amplifier

Figure 79 shows the output voltage and input differential voltage when a 8-V step is applied at the noninverting

terminal of the OPA810 configured as a unity-gain buffer of Figure 78.

Figure 79. Large-Signal Transient Response Using the OPA810

Because of the fast input transient, the amplifier is slew-limited and the inputs cease to track each other (a

maximum VIN,Diff of 7 V is shown in Figure 79) until the output reaches its final value and the negative feedback

loop is closed. For standard amplifiers with a 0.7-V to 1.5-V maximum VIN,Diff rating, current-limiting resistors

must be used in series with the input pins to protect the device from irreversible damage, which also limits the

device frequency response. The OPA810 has built-in input clamps that allow the application of as much as 7 V of

VIN,Diff, with no external resistors required and no damage to the device or a shift in performance specifications.

Such an input-stage architecture, coupled with its fast settling performance, makes the OPA810 a good fit for

multichannel sensor multiplexed systems.

OPA607 数据表(PDF) 33 Page - Texas Instruments

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