Texas Instruments TPA6120A2, Руководство пользователя

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Inverting Configuration
3-2
3.1 Inverting Configuration
The TPA6120A2 EVM can be converted to operate in an inverting gain
configuration. To do this, it is necessary to remove resistors R11 and R12, then
connect the audio source to RCA jacks LIN− (J3) and RIN− (J4) instead of LIN+
(J5) and RIN+ (J6). With the feedback and input resistors already in place on
the EVM, the gain is set to −1 V/V (R
F
/R
I
).
3.2 Differential Configuration
The TPA6120A2 EVM can also be converted to operate in a differential input
configuration. Remove resistors R11 and R12. Resistors R9 and R10 must be
removed and replaced with resistors whose values match those of resistors
R3 and R4, respectively. The 49.9-
Ω
input series resistors, R7 and R8 must
likewise be removed and replaced with resistors whose values match those
of input resistors R1 and R2, respectively. Both positive and negative input
jacks should be used. Assuming the feedback resistors R9 and R3 are equal,
and R10 and R4 are equal, and the input resistors R7 and R1 are equal, and
R8 and R2 are equal, the gain is set by the following formula:
Gain
+
2
R
F
R
I
3.3 Special Note on Gain and Input Configurations
The TPA6120A2 high-fidelity audio power amplifier has two separate
channels, left and right. It is not necessary to operate each channel in the same
configuration. For test purposes, it may be desirable to operate the left channel
with a noninverting configuration, and the right channel with an inverting
configuration. One channel may be configured to operate with differential
inputs while the other channel with single-ended inputs. The TPA6120A2 EVM
allows for this flexibility. From a listening standpoint, the best audio
performance is achieved when both channels are operated with the same
configuration. In this case, there is no sound difference between the left and
right channels for the human ear to detect.
3.4 Single Power Supply Configuration
The TPA6120A2 EVM was not optimized for single power supply operation.
To operate in this mode, the −12-V terminal must be connected to GND.
DC-blocking capacitors must be used at the outputs to prevent large amounts
of dc current from flowing through the headphones due to the high midrail bias.
Likewise, dc-blocking capacitors must be used at the input. Resistors R11 and
R12, and resistors R9 and R10 must be removed. The positive input nodes
must be biased to midrail. Resistors R9 and R10 tie the positive node to
ground.