TI Debuts Octal, Low-Noise Variable Gain Amplifier for Scanning Apps

12/15/2003 - Texas Instruments Incorporated (TI) (NYSE: TXN) announced an eight-channel, low-noise variable gain amplifier from the company´s Burr-Brown product line which is designed specifically for medical and industrial imaging applications, such as portable ultrasound and industrial scanning.

The VCA8613 incorporates eight low-noise preamplifiers, eight attenuators and eight post-gain amplifiers. Normally, this functionality and integration would demand substantial power, but the VCA8613 draws only 600mW (75mW/channel), making it the lowest power solution available on the market today.

"The VCA8613 is all about integration. Eight low-noise preamplifiers, voltage-controlled attenuators and output filters, as well as integration of the space consuming V-I converters and switch matrix for CW Doppler processing make this the highest density solution available on the market," said Ed Fullman, product marketing manager for TI's high-speed data converter products.

Inside the VCA8613
Each channel of the octal VCA8613 consists of a low-noise preamplifier (LNA), a voltage-controlled attenuator (VCA) and a programmable gain amplifier (PGA). The differential outputs of the LNAs can be switched through the 8 x 10 cross-point switch, which is programmable through the serial interface input port. The output of the LNA is fed directly into the VGA. The device operates on a single +3V supply and features 1.2nV/rtHz input voltage noise at 5MHz.

The gain range of the PGA can be digitally configured separately and the gain can be varied between two discrete settings of 21dB and 26dB. The VCA has four programmable maximum attenuation settings: 29dB, 33dB, 36.5dB and 40dB.

The output of the PGA feeds directly into an integrated two-pole, low-pass filter, allowing direct connection to a differential input analog-to-digital converter, such as the ADS5121 and ADS5122 from Texas Instruments.

The VCA8613 features an integrated continuous wave (CW) processor, which allows a dramatic reduction in the number of external components required to support the CW Doppler mode (critical in cardio scanning applications).

Available Today
The VCA8613 is packaged in a TQFP-64, and is available now from TI and its authorized distributors. The device is priced from $25.40 in 1,000 piece quantities (suggested resale pricing). Evaluation modules (EVMs) are also available.

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