TEA-2025 ST Microelectronics, TEA-2025 Datasheet - Page 5

• Manufacturer Part Number: TEA-2025
• Description: STEREO AUDIO AMPLIFIER
• Manufacturer: ST Microelectronics

Figure 7
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:
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
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.
V
V
OUT
IN
Rf
R2
R1
JWC1
1
The total gain of the bridge is given by:
and with the suggested values (C1 = C2 = 100 F,
Rf= 0) means:
Gv = 52 dB
Figure 8
with first pole at f = 32 Hz
Output Capacitors.
The low cut off frequency due to output capacitor
depending on the load is given by:
with C
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 TEA 2025B solution allows to save compo-
nents because of such resistors (800 ohm)are in-
cluded into the chip.
V
V
OUT
IN
OUT
Rf R2
470 F and R
R1
F
L
JWC1
1
2
TEA2025B - TEA2025D
C
L
1
OUT
= 4 ohm it means F
1
R3
R4
R
R2 R4
L
R1
JWC1
1
L
5/9
=