7 Detailed Description

7.1 Overview

The PGA854 is a monolithic, high-voltage, precision programmable-gain instrumentation amplifier. The PGA854

combines a high-speed current-feedback input stage with an internally matched gain resistor network, followed

by a four-resistor, difference amplifier output stage. Eight preprogrammed decade gains are selectable using

gain-select pins A0, A1, A2. Gains range from 0.5V/V to 100V/V; see also Section 7.3.1.

A functional block diagram for the PGA854 is shown in the next section. The differential input voltage is fed

into a pair of matched, high-impedance input, current-feedback amplifiers. An integrated precision-matched gain

resistor network is used to amplify the differential input voltage. An output difference amplifier, A3, rejects the

input common-mode component and refers the output signal to the voltage level set by the VOCM pin.

The PGA854 output amplifier bandwidth is optimized to drive high-performance analog-to-digital converters

(ADCs) with sampling rates up to 1MSPS without additional ADC drivers. The output amplifier uses a separate

power supply that is independent of the input-stage power supply. When driving an ADC, use a low-impedance

connection from LVDD and LVSS to the ADC power supplies. This configuration protects the ADC inputs from

damage resulting from inadvertent overvoltage conditions.

7.2 Functional Block Diagram

+

–

IN

IN+

+

–

6.67k

3.33k

3.33k

+

– +

–

6.67k

A<2:0>

DGND

DGND

VS+

A1

A2

A3

OUT+

LVSS

LVDD

LVSS

LVDD

OUT

FDA_IN–

FDA_IN+

VS+

VS

VOCM

500k

500k

VS+

VS

LVDD

LVSS

VS+

VS

VS+

VS

VS+ VS

VS+

VS

VS+

VS

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PGA854

SBOSAN2A – AUGUST 2025 – REVISED DECEMBER 2025

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