AD9273八进制的低噪声放大器VGA/AAF/ADC纵横式开关系统

　　The AD9273 is designed for low cost， low power， small size， and ease of use. It contains eight channels of a low noise preamplifier （LNA） with a variable gain amplifier （VGA）; an antialiasing filter （AAF）; and a 12-bit， 10 MSPS to 50 MSPS analog-todigital converter （ADC）。 Each channel features a variable gain range of 42 dB， a fully differential signal path， an active input preamplifier termination， a maximum gain of up to 52 dB， and an ADC with a conversion rate of up to 50 MSPS. The channel is optimized for dynamic performance and low power in applications where a small package size is critical.

　　The LNA has a single-ended-to-differential gain that is selectable through the SPI. The LNA input-referred noise voltage is typically 1.26 nV/√Hz at a gain of 21.3 dB， and the combined input-referred noise voltage of the entire channel is 1.42 nV/√Hz at typical gain. Assuming a 15 MHz noise bandwidth （NBW） and a 21.3 dB LNA gain， the input SNR is about 91 dB. In CW Doppler mode， the LNA output drives a transconductance amp that is switched through an 8 × 8 differential crosspoint switch. The switch is programmable through the SPI.