4-channel single-ended output amplifier circuit composed of TDA8580J

The typical application circuit of the 4-channel single-ended output amplifier composed of TDA8580J is shown in the figure below. It is often used in 4-channel stereo amplifiers for car audio. Although the gain and input resistance of the 4 groups of amplifiers are the same, the input driving methods are different from each other, so the phase of the output ends is also different from each other. Among them, OA1 and OA4 are in-phase amplification, and OA2 and OA3 are inverting amplification. When forming a 4-channel surround sound field, the output of the front RL channel and the output of the rear surround left and right must be in phase, so that the main channel and surround channel sound waves have the same phase. Therefore, when matching speakers, it should be noted that when the (+) end of the speaker (some speakers are only marked with a color dot as the (+) end) is connected to pins ④ and 14, the other two speakers should connect the (one) end (or the end without a color dot) to the amplifier's pins ① and 17. For 4 groups of two-channel amplification without a surround sound field, the sound of the 4 speakers also needs to be in the same phase.

The 9th pin of TDA8580J has a low-impedance 1/2Vp output terminal, whose DC voltage to ground is Vp/2, and the AC impedance to ground is approximately zero. The static voltage of the four single-ended output terminals is also Vp/2. Therefore, there is no DC potential difference at both ends of the four sets of speakers, only AC signals, so even though it is a single-ended output, there is no need to connect a large-capacity DC blocking capacitor. This new Philips technology is actually formed by making the output stage DC circuit and AC output circuit independent of each other in the integrated amplifier.