Tripath Technology, Inc. - Technical Information
It should be noted that only one channel of the modulator is required to create a bridged amplifier.
This is done by reversing the Y1 and Y1B connections to the second FET driver. This creates an out
of phase signal at HB OUTN with respect to HB OUTP.
A bridged amplifier has the advantage of potentially 4 times the output power for a given supply rail.
But the disadvantage is that the required number of FET drivers and MOSFETs per channel
increases by a factor of two.
The modulator feedback resistors are:
R
FBA = User specified, typically 1KΩ
R
FBA * VPP
R
FBB
=
(VPP - 2)
R
FBA * VPP
R
A
FBC
=
2
R
FBC * (RFBA + RFBB )
V - MODULATOR
≈
+ 1
R
FBA * RFBB
The above equations assume that VPP=|VNN|.
For example, in a system with a SPLIT-SUPPLY, BRIDGED OUTPUT amplifier of VPPMAX=60V and
VNNMAX=-60V,
RFBA = 1kΩ, 1%
R
FBB = 1.071kΩ, use 1.07kΩ, 1%
RFBC = 15.0kΩ, use 15.0kΩ, 1%
The resultant modulator gain is:
15.0k Ω * (1.0k Ω + 1.07k Ω)
AV - MODULATOR
≈
+ 1 = 30.02V/V
1.0k Ω * 1.07k Ω
For SINGLE-SUPPLY, BRIDGED OUTPUT operation:
VPP
MOSFETS
FET Driver
TCA2002
HB OUTP
HS GATE1
LS GATE1
HIN1
LIN1
HS OUT1
LS OUT1
Y1
Y1B
HS GATE2
LS GATE2
HIN2
LIN2
HS OUT2
LS OUT2
HB OUTN
FBKP1 FBKN1
V5
RFBA
RFBC
RFBB
V5
RFBA
RFBC
RFBB
Figure 5: Single Supply, Bridged Output (One Channel)
12
TCA2002 – KLi/0.95/04.06
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
