Tripath Technology, Inc. - Technical Information
Bridging the TA2022
The TA2022 can be bridged by returning the signal from OAOUT1 to the input resistor at INV2.
OUT1 will then be a gained version of OAOUT1, and OUT2 will be a gained and inverted version of
OAOUT1 (see Figure 3). When the two amplifier outputs are bridged, the apparent load impedance
seen by each output is halved, so the minimum recommended impedance for bridged operation is 8
ohms. Due to the internal current limit setting, the maximum supply voltage recommended for
bridged operation is +/-30V. Bridged operation into loads below 8ohms is possible, but, as mentioned
above, the amplifier efficiency will be reduced and the amplifier may prematurely current limit. The
TA2022 is capable of 150W into 8 ohms bridged at 0.1% THD+N.
TA2022
OAOUT1
V5
RF
CI
RI
-
+
INV1
INPUT
BIASCAP
AGND
V5
20k
20k
+
-
INV2
AGND
OAOUT2
Figure 4: Input Stage Setup for Bridging
The switching outputs, OUT1 and OUT2, are not synchronized, so a common inductor may not be
used with a bridged TA2022. For this same reason, individual zobel networks must be applied to
each output to load each output and lower the Q of each common mode differential LC filter.
Output Voltage Offset
The output offset voltage of the TA2022 is largely determined by the matching of the respective RFBA
,
RFBB, and RFBC networks for FBKOUT1(FBKOUT2) and FBKGND1 (FBKOUT2). Thus, the intrinsic
offset of the TA2022 can be altered by the external feedback network resistor matching. To minimize
the nominal untrimmed offset voltage, 1% tolerance resistors are recommended.
In most applications, the output offset voltage will need to be trimmed via an external circuit (either
passive or active). The output offset voltage of the TA2022 can be nulled by modifying the modulator
feedback as shown in Figure 4. Potentiometer ROFA is used to trim the effective resistance seen by
the output ground, and therefore the output offset. ROFB limits the trim range.
19
TA2022 – KLI/1.2/07-04
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
