Datasheet

S0501-01
I/VSum
Amp
CW_AMPINP CW_OUTM
CW_AMPINM CW_OUTP
C
EXT
C
EXT
R
EXT
R
EXT
R
INT
R
INT
2000Ω
2000Ω
1000Ω
1000Ω
500Ω
500Ω
250Ω
250Ω
250Ω
250Ω
AFE5808A
SLOS729B –OCTOBER 2011–REVISED APRIL 2012 www.ti.com
Figure 87. CW Summing Amplifier Block Diagram
Multiple AFE5808As are usually utilized in parallel to expand CW beamformer channel count. These AFE5808As’
CW outputs can be summed and filtered externally further to achieve desired gain and filter response. AC
coupling capacitors C
AC
are required to block DC component of the CW carrier signal. C
AC
can vary from 1 µF to
10s μF depending on the desired low frequency Doppler signal from slow blood flow. Multiple AFE5808As’ I/Q
outputs can be summed together with a low noise external differential amplifiers before 16/18-bit differential
audio ADCs. TI’s ultralow noise differential precision amplifier OPA1632 and THS4130 are suitable devices.
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