SIGNAL CHAIN BASICS #68: Considerations for driving the reference pins on programmable gain amplifiers
(Editor’s note: Signal Chain Basics is an ongoing series; click here for a complete, linked list of all installments.)
Programmable gain amplifiers (PGAs) are specialized amplifier configurations with trimmed internal resistor networks that offer improved performance over amplifiers used with discrete resistor components.
The absolute error at the PGA output is a function of the internal offset voltage (VOS), gain accuracy, and absolute accuracy of VREF.
The accuracy of the PGA transfer function can be significantly impacted if the reference pin, VREF, is not driven by an op amp buffer. Furthermore, from an AC standpoint, one of the common challenges is maintaining gain accuracy over frequency, which will be affected by the voltage at the reference pin, VREF, and the op amp that buffers it.
What considerations should the designer have when driving the reference pins on programmable gain amplifiers.
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