Tripath Technology, Inc. - Technical Information
Bridged Operation
Note that the two channels of a TA0102A amplifier can be used to provide a single, bridged amplifier
of almost four times the output power of one of the single-ended amplifier channels. To configure a
bridged amplifier, the input to one TA0102A channel must be the inverted signal of the input to the
other channel.
Low-frequency Power Supply Pumping
A potentially troublesome phenomenon in single-ended switching amplifiers is power supply
pumping. This is caused by current from the output filter inductor flowing into the power supply
output filter capacitors in the opposite direction as a DC load would drain current from them. Under
certain conditions (usually low-frequency input signals), this current can cause the supply voltage to
“pump” (increase in magnitude) and eventually cause over-voltage/under-voltage shut down.
Moreover, since over/under-voltage are not “latched” shutdowns, the effect would be an amplifier
that oscillates between on and off states. If a DC offset on the order of 0.3V is allowed to develop on
the output of the amplifier (see “DC Offset Adjust”), the supplies can be boosted to the point where
the amplifier’s over-voltage protection triggers.
One solution to the pumping issue is to use large power supply capacitors to absorb the pumped
supply current without significant voltage boost. The low frequency pole used at the input to the
driver determines the value of the supply capacitor required. This works for AC signals only.
Another solution to the supply pumping problem uses the fact that music has low frequency
information that is correlated in both channels (it is in phase). This information can be used to
eliminate boost by putting the two channels of a TA0102A amplifier out of phase with each other.
This works because each channel is pumping out of phase with the other, and the net effect is a
cancellation of pumping currents. The phase of the audio signals needs to be corrected by
connecting one of the speakers in the opposite polarity as the other channel.
CONTACT INFORMATION
World Wide Sales Offices
United States & Europe
SE Asia & China
Jim Hauer
Eugene Hsu
Osamu Ito
jhauer@tripath.com
ehsu@tripath.com
ito@tripath.com
408.567.3089
886.2.2653.7428
81.42.334.2433
Japan & Korea
T R I P A T H T E C H N O L O G Y , I N C
3900 Freedom Circle
Santa Clara
4C0A89.5506574.3000
www.tripath.com
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TA0102A, Rev. 3.1/06.01
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
