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Analog Devices (ADI), a provider of high-speed amplifiers, has introduced the AD8264 quad-channel variable-gain amplifier (VGA).

The AD8264 VGA is a highly integrated device designed for positron emission tomography (PET) scanners, communication systems and advanced video equipment.

It is the first VGA to integrate four analogue-to-digital converter (ADC) drivers, enabling radiological equipment designers, for example, to reduce printed-circuit board area and simplify layout by replacing eight components with a single device.

Space saving is a key design requirement for advanced systems in many applications.

Next-generation PET scanner designs are increasing channel densities to enhance image resolution and improve patient diagnostics, despite limits to the physical size of the scanning element or gantry.

The high-speed AD8264 VGA has a single-ended output for wide-bandwidth applications and auxiliary differential ADC drivers that operate with ADI’s data converters, including the AD9222 octal and AD9228 quad 12-bit ADCs.

The AD8264 quad VGA is also said to be suited for wireless infrastructure equipment where its four DC-coupled channels and precise gain control allow communication systems designers to more easily adjust output-signal levels and eliminate the time and cost associated with matching four discrete VGAs.

For advanced broadcast and video-security applications, the VGA is claimed to improve picture quality by more accurately white-balancing red, green and blue (RGB) signals and better managing gain-trim calibration over the system’s life.

Each of the AD8264’s four linear-in-dB VGA channels has independent gain control.

Each channel comprises a high-impedance pre-amplifier, a high-speed VGA and a differential output amplifier.

The AD8264’s pin-out provides single-ended output taps directly from the VGAs, which have a -3dB bandwidth of 235MHz and balanced outputs from the 80MHz output amplifiers.

Dual-supply operation enables gain control of negative-going pulses such as those that are generated by photodiodes, photo-multiplier tubes and video signal sources.

With a 24dB gain range, the AD8264 features a gain-control interface that provides a precise 20dB/V linear-in-dB scale.

A common gain-control reference for all channels is intended to simplify wiring.

The differential gain-control structure accommodates a wide range of common-mode operating points, simplifying the interface to any analogue or digital control source.

A VOCM pin sets the common-mode voltage of the differential output stage to match modern single-supply ADCs and allows for dc-level shift of the output.

Power consumption is 125MW per channel at +/-3.3V.

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