EUA6204A
Input Capacitor (C
I
)
The EUA6204A does not require input coupling
capacitors if using a differential input source that is
biased from 0.5V to V
DD
-0.8V. Use 1% tolerance or
better gain-setting resistors if not using input coupling
capacitors.
In the single-ended input application an input capacitor,
C
I
, is required to allow the amplifier to bias the input
signal to the proper dc level. In this case, C
I
and R
I
form
a high-pass filter with the corner frequency determined
in equation3.
1
f
=
(3)
C 2π R C
I I
Decoupling Capacitor (C
S
)
The EUA6204A is a high-performance CMOS audio
amplifier that requires adequate power supply
decoupling to ensure the output total harmonic distortion
(THD) is as low as possible. Power supply decoupling
also prevents oscillations for long lead lengths between
the amplifier and the speaker. For higher frequency
transients, spikes, or digital hash on the line, a good low
equivalent-series-resistance (ESR) ceramic capacitor,
typically 0.1µF to 1 µF, placed as close as possible to the
device V
DD
lead works best. For filtering lower
frequency noise signals, a 10-µF or greater capacitor
placed near the audio power amplifier also helps, but is
not required in most applications because of the high
PSRR of this device.
The value of C
I
is important to consider as it directly
affects the bass (low frequency) performance of the
circuit.
Consider the example where R
I
is 10kΩ and the
specification calls for a flat bass response down to
100Hz. Equation 3 is reconfigured as equation4.
1
C
=
(4)
I 2π R f
I C
In this example, C
I
is 0.16µF, so one would likely
choose a value in the range of 0.22µF to 0.47µF.
Ceramic capacitors should be used when possible, as
they are the best choice in preventing leakage current.
When polarized capacitors are used, the positive side of
the capacitor should face the amplifier input in most
applications, as the dc level there is held at V
DD
/2, which
is likely higher than the source dc level. It is important to
confirm the capacitor polarity in the application.
DS6204A Ver 1.2 Jan. 2007
10
EUTECH [ EUTECH MICROELECTRONICS INC ]
