TEA2025B - TEA2025D
APPLICATION INFORMATION
Input Capacitor
Input capacitor is PNP type allowing source to be
referenced to ground.
In this way no input coupling capacitor is required.
However, a series capacitor (0.22 uF)to the input
side can be useful in case of noise due to variable
resistor contact.
Bootstrap
The bootstrap connection allows to increase the
output swing.
The suggested value for the bootstrap capacitors
(100uF) avoids a reduction of the output signal
also at low frequencies and low supply voltages.
Voltage Gain Adjust
STEREO MODE
The voltage gain is determined by on-chip resis-
tors R1 and R2 together with the external RfC1
series connected between pin 6 (11) and ground.
The frequency response is given approximated
by:
1
Rf
+
R2
+
JWC1
With Rf=0, C1=100 uF, the gain results 46 dB
with pole at f=32 Hz.
THE purpose of Rf is to reduce the gain. It is rec-
ommended to not reduce it under 36 dB.
BRIDGE MODE
Figure 7
V
OUT
=
V
IN
R1
Output Capacitors.
The low cut off frequency due to output capacitor
depending on the load is given by:
F
L
=
2
ΠC
OUT
•
R
L
1
The total gain of the bridge is given by:
)
1
1
R2+R4+
Rf+R2
+
JWC1
JWC1
and with the suggested values (C1 = C2 = 100
µF,
Rf= 0) means:
Gv = 52 dB
(1+
Figure 8
V
OUT
=
V
IN
R1
R3
R4
R1
with first pole at f = 32 Hz
with C
OUT
470µF and R
L
= 4 ohm it means F
L
=
80 Hz.
Pop Noise
Most amplifiers similar to TEA 2025B need exter-
nal resistors between DC outputs and ground in
order to optimize the pop on/off performance and
crossover distortion.
Figure 9
The bridge configuration is realized very easily
thanks to an internal voltage divider which pro-
vides (at pin 1) the CH 1 output signal after reduc-
tion. It is enough to connect pin 6 (inverting input
of CH 2) with a capacitor to pin 1 and to connect
to ground the pin 7.
The TEA 2025B solution allows to save compo-
nents because of such resistors (800 ohm)are in-
cluded into the chip.
5/9
STMICROELECTRONICS [ STMICROELECTRONICS ]
