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News Release from: Analog Devices
Edited by the Electronicstalk Editorial Team on 26 June 2006

VGA boasts big gain and bandwidth

A DC-coupled variable-gain amplifier claims the industry's highest gain and bandwidth.

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Analog Devices has introduced a DC-coupled VGA (variable-gain amplifier) that claims the industry's highest gain and bandwidth. The AD8336 is also the only VGA that supports an extended industrial temperature range and a wide power supply range from +/-3 to +/-12V - the voltage range used in industrial and instrumentation applications such as industrial process control, high-performance automatic-gain control, industrial video systems, transducer and display drivers, and radar receivers. The device's combination of gain, bandwidth, wide operating temperature range and wide supply voltage range gives designers more flexibility than any VGA in its class.

Competing solutions, in comparison, are typically module based or require two or more cascaded VGAs to provide similar gain range - with both options adding to materials cost and board area.

Designed for high-voltage and wide temperature applications, the AD8336 VGA provides 100MHz bandwidth over a gain range of 60dB, more than twice the bandwidth of competing VGAs that operate at much lower supply voltages.

The AD8336 includes a voltage feedback op amp at its input that allows the gain to be externally adjusted.

The nominal pre-amp gain is 4x (12dB); a gain of 20x (26dB) can be obtained at a reduced bandwidth.

The AD8336 operates at a maximum gain range of 0 to 60dB with the pre-amp gain set to 26dB.

Unlike competing dc-coupled VGAs, whose bandwidth degrades as gain increases, the AD8336 provides 100MHz performance over the 60dB gain range - from -14 to +46dB.

The low input referred noise of 3.2nV/(rt)Hz allows the VGA to process very small signals and the large usable supplies expand the dynamic range by a factor of four (12dB) from +/-3 to +/-12V, as the noise level stays the same for all supplies.

The AD8336 also operates over the extended industrial temperature range of -55 to +125C with unequalled precision, and a power-adjust pin allows power to be traded for speed in applications that need large supply voltages yet where slower speed is acceptable.

'Designers of single-ended industrial and instrumentation systems who need VGAs require good AC and DC performance over temperature and wide power supply ranges', said Steve Sockolov, Product Line Director, Precision Linear Products Group, Analog Devices.

'However, most VGAs available on the market today are designed with RF applications in mind and operate on single supplies'.

'The AD8336 is the first VGA capable of processing high frequency bipolar signals at high gain'.

'It meets the demands of the industrial marketplace for a VGA with outstanding AC performance combined with stable DC characteristics over a broad temperature range and power supply voltages from +/-3 to +/-12V'.

The AD8336 features low power of 150mW at a +/-3V supply, low noise of 3.2nV/(rt)Hz, low output offset of less than 50mV at maximum gain and a slew rate of 450V/us for a 2V step.

The inclusion of a voltage feedback op amp at its input allows the AD8336 to accommodate both inverting and noninverting topologies, and thereby, a dual polarity VGA.

The pre-amp gain can be set from 12 to 26dB.

The AD8336 is suitable for use with analogue-to-digital convertors (ADCs) such as the AD7656, AD7634, AD7951, and AD9460.

The new VGA can be controlled by many types of digital-to-analogue convertors (DACs), including unipolar and bipolar DACs, as the gain control input is differential to the AD8336 and the gain control common-mode voltage increases with increasing supply.

Compatible DACs include the 8bit AD5300 and AD5330 and the 10bit AD5331 and AD5338 in space-constrained applications.

The AD8336 is sampling now and available in a 4 x 4mm, 16-lead LFCSP (lead-frame chip-scale package) and will be available in volume production in October 2006.

The VGA is priced at $4.59 in 1000-piece quantities.

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