OPA4872-EP_12 Datasheet, PDF (12/25 Pages) Texas Instruments – 4:1 HIGH-SPEED MULTIPLEXER

OPA4872-EP
SBOS444 – DECEMBER 2008........................................................................................................................................................................................... www.ti.com
2-BIT HIGH-SPEED PGA
The OPA4872 can be used as a 2-bit, high-speed
programmable gain amplifier (PGA) when used in
conjunction with another amplifier. Figure 28 shows
one OPA695 used in series with each OPA4876 input
and configured with gains of +1 V/V, +2 V/V, +4 V/V,
and +8 V/V, respectively.
When channel 0 is selected, the overall gain to the
matched load of the OPA4872 is 0dB. When channel
1 is selected, this circuit delivers 6 dB of gain to the
matched load. When channel 2 is selected, this circuit
delivers 12 dB of gain to the matched load. When
channel 3 is selected, this circuit delivers 18 dB of
gain to the matched load.
+5V
OPA695
50W
G = 1V/V
-5V
523W
50W
+5V
+5V
IN0
OPA4872
OPA695
50W
G = 2V/V
-5V
511W
IN1
511W
+5V
OPA695
-5V
453W
149W
+5V
OPA695
-5V
402W
IN2
50W
G = 4V/V
IN3
50W
G = 8V/V
Logic
A0 A1
-5V
SD
EN
50W
523W _{To 50W Load}
523W
57.6W
Figure 28. 2-Bit, High-Speed PGA, Greater Than 300MHz Channel Bandwidth
12
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