Texas Instruments APA100 - Manual (Page 22)

Changing the Gain
3-4
3.5 Changing the Gain
The APA100 EVM is set with a gain of 31.4 dB, but can be adjusted. The
front-end has a gain of 4.4 dB (−1.667 V/V), and a back-end gain of 27 dB
(−22.4 V/V), for a total of 31.4 dB (37.3 V/V). The back-end gain needs to be
kept constant, because it is set by the control-loop feedback system with the
TLV2464A, TPA2001D1, and TAS5111. The front-end gain is set by section A
of the quad operational amplifier TLV2464A. The front-end gain is set by
Equation 1, which is a ratio of feedback to input resistors.
Front−end Gain
+ * R4
(R5
)
R6)
(V
ń
V)
(1)
The APA100 EVM total gain can then be set by multiplying the front-end and
back-end gains, as shown in Equation 2.
(2)
Total Gain
+
22.4
R4
(R5
)
R6)
(V
ń
V)