Datasheet

SUMMING INPUT SIGNALS WITH THE TPA2006D1
Summing Two Differential Input Signals
Gain 1 +
V
O
V
I1
+
2 x 150 kW
R
I1
ǒ
V
V
Ǔ
(4)
Gain 2 +
V
O
V
I2
+
2 x 150 kW
R
I2
ǒ
V
V
Ǔ
(5)
Filter-FreeClassD
SHUTDOWN
TPA2006D1
SLOS498A – SEPTEMBER 2006 – REVISED JULY 2008 ................................................................................................................................................. www.ti.com
Most wireless phones or PDAs need to sum signals at the audio power amplifier or just have two signal sources
that need separate gain. The TPA2006D1 makes it easy to sum signals or use separate signal sources with
different gains. Many phones now use the same speaker for the earpiece and ringer, where the wireless phone
would require a much lower gain for the phone earpiece than for the ringer. PDAs and phones that have stereo
headphones require summing of the right and left channels to output the stereo signal to the mono speaker.
Two extra resistors are needed for summing differential signals (a total of 5 components). The gain for each input
source can be set independently (see Equation 4 and Equation 5 , and Figure 30 ).
If summing left and right inputs with a gain of 1 V/V, use R
I1
= R
I2
= 300 k Ω .
Figure 30. Application Schematic With TPA2006D1 Summing Two Differential Inputs
12 Submit Documentation Feedback Copyright © 2006 – 2008, Texas Instruments Incorporated
Product Folder Link(s): TPA2006D1