The VCA8613 is an 8-channel variable gain amplifier ideally suited to portable ultrasound applications. Excellent dynamic performance enables use in low-power, high-performance portable applications. Each channel consists of a Low-Noise pre-Amplifier (LNA) and a Variable Gain Amplifier (VGA). The differential outputs of the LNA can be switched through the 8x10 cross-point switch, which is programmable through the serial interface port.
The output of the LNA is fed directly into the VGA stage. The VGA consists of two parts, a Voltage Controlled Attenuator (VCA) and a Programmable Gain Amplifier (PGA). The gain and gain range of the PGA can be digitally configured separately. The gain of the PGA 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. Also, the VCA can be continuously varied by a control voltage from 0dB to a maximum of 29dB, 33dB, 36.5dB, and 40dB.
The output of the PGA feeds directly into an integrated 2-pole, low-pass filter, allowing for direct connection to a differential input Analog-to-Digital Converter (ADC), such as the ADS5121 or ADS5122 from Texas Instruments. The VCA8613 is available in a TQFP-64 package.
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