The PGA848 is a monolithic, high-voltage, precision programmable-gain instrumentation amplifier. The PGA848 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, and A2. Gains range from 0.5V/V to 100V/V, discussed in greater detail in Section 7.3.1.

A functional block diagram for the PGA848 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 amplifies 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 REF pin.

The PGA848 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.