6W/8Ω power amplifier based on TDA1521

Rohit Balkishan Dubla

Figure 1 shows the amplifier schematic. It is based on the 12 + 12W power IC TDA1521 from Philips. The circuit is based on the typical application given in the datasheet but with a few changes as follows:

• 1. Voltage gain is reduced from that used by the typical application. The external gain resistor R1 (R2 for the other channel) is connected to pin 2 (8). Along with the internal 680Ω resistor, this forms a gain resistor of 2.48K thereby reducing the gain. The sensitivity is about 800mV to 1V after adding the resistors. In order to ensure unity gain at DC, capacitor C2 (C3) is connected in series with R1 (R2).

  2. The input capacitors (pins 1 & 9) are changed to 1µF from the original 220nF.

The power supply used is between ±12V to ±15V DC. The supply must be properly decoupled using 100nF decoupling capacitors close to pins 5 and 7. With this, the amplifier will deliver about 6W/channel into an 8Ω load. Also, note that the schematic shown has a different component labelling than that on the datasheet schematic - bear this in mind while comparing the two.