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Service Manual CP-099/FS
5-8 Sound amplification
The TDA8944J (TDA8946J) is a stereo BTL audio amplifier capable of delivering 2 x 5W output power to
an 8 W load at THD = 10%, using a 12 V power supply and an external heatsink. The voltage gain is fixed at 32dB.
With the three-level MODE input the device can be switched from ‘standby’ to ‘mute’ and to ‘operating’ mode.
The TDA 8944J outputs are protected by an internal thermal shutdown protection mechanism and short-circuit
protection.
5-8-1 Power amplifier
The power amplifier is a Bridge Tied Load (BTL) amplifier with an all-NPN output stage, capable of delivering a peak
output current of 1.5 A.
The BTL principle offers the following advantages :
- Lower peak value of the supply current.
- The ripple frequency on the supply voltage is twice the signal frequency.
- No DC-blocking capacitor
- Good low frequency performance
5-8-2 Mode selection
The TDA894xJ has several functional modes, which can be selected by applying the proper DC voltage to pin MODE.
Mute : In this mode the amplifier is DC biased but not operational (no audio output). This allows the input coupling
capacitors to be charged to avoid pop-noise. The device is in mute mode when 2.5 V < V
MODE
< (Vcc-1.5 V).
Operating : In this mode the amplifier is operating normally. The operating mode is activated at V
MODE
< 0.5 V.
5-8-3 Vertical deflection
The vertical driver circuit is a bridge configuration. The deflection coil is connected between the output amplifiers,
which are driven in phase opposition. The differential input circuit is voltage driven. The input circuit is especially
intended for direct connection to driver circuits which deliver symmetrical current signals, but is also suitable for
asymmetrical currents. The output current of these devices is converted to voltages at the input pins via resistors R303
and R304. The differential input voltage is compared with the output current through the deflection coils measured as
voltage across R311, which provides internal feedback information. The voltage across R311 is proportional to the
output current.
5-8-4 Flyback voltage
The flyback voltage is determined by an additional supply voltage V
flb
. The principle of operation with two supply
voltages (class G) makes it possible to fix the supply voltage Vp optimum for the scan voltage and the second supply
voltage V
flb
optimum for the flyback voltage. Using this method, very high efficiency is achieved. The supply voltage
V
flb
is almost totally available as flyback voltage across the coil, this being possible due to the absence of a coupling
capacitor.
5-8-5 Protection
The output circuit has protection circuits for :
- Too high die temperature
- overvoltage of output stage A
Summary of Contents for DDT-21H9ZDF(21")
Page 17: ...16 Service Manual CP 099 FS...
Page 40: ...Service Manual CP 099 FS 39 5 Circuit desription 5 1 Block diagram CP 099...
Page 41: ...Service Manual CP 099 FS 40 5 Circuit desription Block diagram CP 099FS...
Page 66: ...65 CIRCUIT DIAGRAM VE2 0 DVD Player Series Block Diagram...
Page 67: ...66 CIRCUIT DIAGRAM DVD MODULE DQL 1000 ALIM3351 MPEG IC...
Page 68: ...67 CIRCUIT DIAGRAM DVD MODULE DQL 1000 RF MOTOR_DIRIVERS...
Page 69: ...68 CIRCUIT DIAGRAM DQL 1000 FLASH SDRAM...
Page 70: ...69 CIRCUIT DIAGRAM DQL 1000 AUDIO_DAC VIDEO_CHANNEL...
Page 71: ...70 CIRCUIT DIAGRAM DQL 1000 SYSTEM_POWER...
Page 75: ...74 CIRCUIT OPERATIONAL DESCRIPTION b TRACKING Block Diagram c MIRROR Block Diagram...
Page 107: ...Service Manual CP 099 FS 106 8 3 DDT 14H9ZZF...
Page 108: ...Service Manual CP 099 FS 107 9 PRINTED CIRCUIT BOARD 9 1 Main PCB CP 099FS...
Page 109: ...Service Manual CP 099 FS 108 9 2 Main PCB CP 099...
Page 110: ...Service Manual CP 099 FS 9 3 Power PCB CP 099 109...
Page 111: ...Service Manual CP 099 FS 9 4Power PCB CP 099FS 110...
Page 112: ...Service Manual CP 099 FS 111 10 SCHEMATIC DIAGRAM 10 1 Main CP 099...
Page 113: ...Service Manual CP 099 FS 112 Main CP 099FS...
Page 114: ...Service Manual CP 099 FS 113 10 2 Power CP 099FS...
Page 115: ...Service Manual CP 099 FS 114 Power CP 099...
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