5/11
TEA2025
3 APPLICATION INFORMATION
3.1 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 µF)to the input side
can be useful in case of noise due to variable resistor contact.
3.2 Bootstrap
The bootstrap connection allows to increase the output swing.
The suggested value for the bootstrap capacitors (100µF) avoids a reduction of the output signal also at
low frequencies and low supply voltages.
3.3 Voltage Gain Adjust
3.3.1 STEREO MODE
The voltage gain is determined by on-chip resistors R1 and R2 together with the external RfC1 series con-
nected between pin 6 (11) and ground. The frequency response is given approximated
With Rf=0, C1=100 µF, the gain results 46 dB with pole at f=32 Hz.
THE purpose of Rf is to reduce the gain. It is recommended to not reduce it under 36 dB.
3.3.2 BRIDGE MODE
Figure 11.
The bridge configuration is realized very easily thanks to an internal voltage divider which provides (at pin
1) the CH 1 output signal after reduction.
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 total gain of the bridge is given by:
and with the suggested values (C1 = C2 = 100 µF, Rf= 0) means: Gv = 52 dB with first pole at f = 32 Hz
V
OUT
V
IN
--------------
R1
Rf R2
1
JWC1
-----------------+÷
---------------------------------------------=
V
OUT
V
IN
--------------
R1
Rf R2
1
JWC1
-----------------+÷
---------------------------------------------
1
R3
R4
--------
R1
R2 R4
1
JWC1
-----------------++
---------------------------------------------- -
+
⎝⎠
⎜⎟
⎜⎟
⎛⎞
=
