INTEGRATED STEREO AMPLIFIER

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The Type TDA1521 from Valvo/Mullard is an integrated HiFi stereo power amplifier designed for mains fed applications such as stereo TV. The device works optimally when fed from a ± 16V supply, and delivers a maximum output power of 2 x 12W into 8 ohm. The gain of the amplifiers is fixed internally at 30 dB with a spread of 0.2 dB to ensure optimum gain balance between the channels. A special feature of the chip is its built-in mute circuit, which

disconnects the non-inverting inputs when the supply voltage is less than ± 6 V, a level at which the amplifiers are still correctly biased. This arrangement ensures the absence of unwanted clicks and other noise when the amplifier is switched on or off. The TDA1521 is protected against output short circuits and thermal overloading. The SIL9 package should be bolted on to a heat sink with a thermal resistance of no more than 3.3KIW (RL=8Q; Vs=± 16V; Pd=14.6W; Ta=65 °C). Note that the metal tab on the chip package is internally connected to pin 5. The accompanying photograph shows that this high quality stereo amplifier has a very low component count, and is readily constructed on a piece of Veroboard.

The following technical data are stated as typical in the datasheets for the TDA1521 (RL=8 Q; Vs= ± 16 V):

Distortion at Po= 12W:                           0.5%

Quiescent current:                                  40mA

Gain balance:                                         0.2dB

Supply ripple rejection:                           60dB         

Channel separation:                                70dB

Output offset voltage:                             20mV

3 dB power bandwidth:                          20-20,000Hz