Quad variable gain amplifier lowers the power/cost for medical ultrasound systems

Analog Devices is introducing a quad variable gain amplifier (VGA) that enables medical ultrasound engineers to achieve greater image quality while reducing the power, cost and size of new designs. Compared to competitive VGAs now used for low to mid-range and portable systems (10- and 12-bit resolution), the AD8335 delivers 4x better signal-to-noise ratio (SNR) while reducing the size and power consumption per channel by 50%, and cost per channel by 30%.

For optimized performance, the AD8335 provides two key requirements for medical imaging: higher SNR and control of output signal levels. At 92 dB of input SNR, the device offers 10 dB greater dynamic range than the closest competitor. Each of the AD8335's four channels contain an ultra-low noise preamplifier (LNA), an X-AMP VGA, and a gain control interface to optimize gain and power levels. Featuring a single-ended input and differential or single-ended outputs, the LNA provides accurate and optimal noise performance with an active impedance match set by an external feedback resistor. By adjusting the clamping level, the external resistor and selectable output clamping functionality protect against input overload to subsequent ADCs or post-amplifiers.

The AD8335 operates from a single 5-V supply, consuming only 92 mW per channel to meet the low-power requirements of medical ultrasound systems. The VGA is also suitable for other cost and power sensitive systems including industrial test measurement and time-gain control for sonar systems.

Application Diagram
Application Diagram

In addition to the AD8335, Analog Devices offers single- (AD8331) and dual-channel (AD8332) ultra-low noise, linear-in-dB VGAs, which have become the industry's choice for ultrasound systems at frequencies up to 120 MHz. The AD8335 works well with Analog Devices' AD9229 12-bit, quad high-speed ADC.

The AD8335 quad VGA operates over the industrial temperature range of -40 degrees Celsius to +85 degrees Celsius and is available in a 9 mm x 9 mm, 64-lead LFCSP (lead frame chip scale package) for increased board space savings. As per the convention in the medical imaging market, the pricing for the AD8335 is given on a per channel basis, which is $3.00 per channel. The 1k OEM price is therefore $12.00.

AD8335 data sheet

Analog Devices, Inc. Tel: 1-800-ANALOGD (1-800-262-5643)

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