Electronic Design

Something New In PGAs

What do you call a family of 900-kHz, selectable-gain amplifiers that provide a gain-select pin in place of a negative-input pin? Microchip Technology calls it the MCP6G0x family, with single, dual, single with chip select, and quad models. The company offers these devices as drop-in replacements for op amps, as microcontroller-controlled amplifiers, or as standalone gain blocks.

The MCP6G0x amplifiers operate from 1.8 to 5.5 V with a 110-µA quiescent current draw. The bandwidth (BW) depends on the gain you select: 350 kHz for 10 V/V, 250 kHz for 50 V/V, and 1 MHz at 1 V/V.

You select one of those gains by driving the gain-input pin to the high, low, or high-impedance state with the microcontroller or by connecting the pin directly to VCC, VSS, or "No-Connect" for op-amp drop-in replacement or standalone operation (see the figure). Whenever one of the higher gains is selected, the devices adjust their internal compensation, providing greater bandwidth at a lower current.

There are three advantages to using members of the family versus controlling the gain of conventional op amps via a pair of resistors. Most notable is that Microchip's internal resistors are pretrimmed for precise gain control. Gain error is specified as less than 1%, which is better than you'd achieve even with 1% external resistors. The internal resistors also are laid out in consideration of thermal gradient issues to reduce gain error over temperature.

The second advantage is reduced footprint/parts-count. And given that these chips are made by Microchip, the third advantage is that gain is easily controllable by a microcontroller—one pin: high, low, or NC.

Pricing ranges from $0.34 to $0.70 each, all in 10,000-unit lots.

Microchip Technology
www.microchip.com

TAGS: Microchip
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