EUA2005 Datasheet, PDF (10/14 Pages) List of Unclassifed Manufacturers – 1.5-W Mono Filterless Class-D Audio Power Amplifier

EUA2005
Application Information
Fully Differential Amplifier
The EUA2005 is a fully differential amplifier with
differential inputs and outputs. The fully differential
amplifier consists of a differential amplifier and a
common-mode amplifier. The differential amplifier
ensures that the amplifier outputs a differential voltage on
the output that is equal to the differential input times the
gain. The common-mode feedback ensures that the
common-mode voltage at the output is biased around
V_DD/2 regardless of the common-mode voltage at the
input. The fully differential EUA2005 can still be used
with a single-ended input; however, the EUA2005
should be used with differential inputs when in a noisy
environment, like a wireless handset, to ensure maximum
noise rejection.
Advantages of Fully Differential Amplifiers
z Input-coupling capacitors not required:
- The fully differential amplifier allows the inputs to
be biased at voltage other than mid-supply. For
example, if a codec has a midsupply lower than the
midsupply of the EUA2005, the common-mode
feedback circuit will adjust, and the EUA2005 outputs
will still be biased at midsupply of the EUA2005. The
inputs of the EUA2005 can be biased from 0.5V to
V_DD – 0.8 V. If the inputs are biased outside of that
range, input-coupling capacitors are required.
z Midsupply bypass capacitor, C_(BYPASS), not required:
- The fully differential amplifier does not require a
bypass capacitor. This is because any shift in the
midsupply affects both positive and negative channels
equally and cancels at the differential output.
z Better RF−immunity:
-GSM handsets save power by turning on and shutting
off the RF transmitter at a rate of 217 Hz. The
transmitted signal is picked-up on input and output
traces. The fully differential amplifier cancels the
signal much better than the typical audio amplifier.
Component Selection
Figure 23 shows the EUA2005 typical schematic with
differential inputs and Figure 24 shows the EUA2005
with differential inputs and input capacitors, and Figure
25 shows the EUA2005 with single-ended inputs.
Differential inputs should be used whenever possible
because the single-ended inputs are much more
susceptible to noise.
Table 1. Typical Component Values
REF DES
VALUE
R_I
150kΩ ( ± 0.5%)
C_S
1µF (+22%,-80%)
C_I (1)
3.3nF ( ^± 10%)
(1) C_I is only needed for single-ended input or if V_ICM is not
between 0.5 V and V_DD – 0.8 V. C_I = 3.3 nF (with R_I = 150
kΩ) gives a high-pass corner frequency of 321 Hz.
Figure 23. Typical Application Schematic With
Differential Input for a Wireless Phone
Figure 24. Typical Application Schematic With
Differential Input and Input Capacitors
DS2005 Ver 1.1 Nov. 2006
Figure 25. Typical Application Schematic With
Single-Ended Input
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