EUA6204A
Application Information
Application Schematics
Figure17 through Figure18 show application schematics
for differential and single-ended inputs. Typical values
are shown in Table1.
Table1. Typical Component Value
Component
R
I
C
(BYPASS)
C
S
C
I
Value
40kΩ
0.22µF
1µF
0.22µF
Power Dissipation
Power dissipation is a major concern when designing a
successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased
power delivered to the load by a bridge amplifier is an
increase in internal power dissipation. Since the
EUA6204A has two operational amplifiers in one package,
the maximum internal power dissipation is 4 times that of
a single-ended amplifier. The maximum power dissipation
for a given application can be derived from the power
dissipation graphs of from equation1.
P
DMAX
=
4 * (V
DD
)
2
/(2π
2
R
L
)
------------(1)
It is critical that the maximum junction temperature T
JMAX
of 150°C is not exceeded. T
JMAX
can be determine from
the power derating curves by using P
DMAX
and the PC
board foil area. By adding additional copper foil, the
thermal resistance of the application can be reduced,
resulting in higher P
DMAX.
Additional copper foil can be
added to any of the leads connected to the EUA6204A. If
T
JMAX
still exceeds 150°C, then additional changes must
be made. These changes can include reduced supply
voltage, higher load impedance, or reduced ambient
temperature. Internal power dissipation is a function of
output power.
Proper Selection of External Components
Gain-Setting Resistor Selection
The input resistor (R
I
) can be selected to set the gain of
the amplifier according to equation2.
Gain=R
F
/R
I
(2)
The internal feedback resistors (R
F
) are trimmed to 40kΩ.
Resistor matching is very important in fully differential
amplifiers. The balance of the output on the reference
voltage depends on matched ratios of the resistors. CMRR,
PSRR, and the cancellation of the second harmonic
distortion diminishes if resistor mismatch occurs.
Therefore, it is recommended to use 1% tolerance
resistors or better to keep the performance optimized.
Bypass Capacitor (C
BYPASS
) and Start-up Time
The internal voltage divider at the Bypass pin of this
device sets a mid-supply voltage for internal references
and sets the output common mode voltage to V
DD
/2.
Adding a capacitor to this pin filters any noise into this
pin and increases k
SVR.
C
(BYPASS)
also determines the rise
time of V
O+
and V
O-
when the device is taken out of
shutdown. The larger the capacitor, the slower the rise
time. Show the relationship of C
(BYPASS)
to start-up time as
Figure13.
DS6204A Ver 1.2 Jan. 2007
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
