A simple UMZCH on a TDA7294 chip. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
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Readers are offered one version of the amplifier, in which a typical TDA7294 switching circuit is used. The main technical characteristics of the amplifier (Fig. 1) are as follows: input impedance - 22 kOhm; input voltage - 750 mV; rated output power at a load of 4 ohms and with a harmonic coefficient of 0,5% - 70 W; reproducible frequency range - 20...20000 Hz; supply voltage - ±27 V; quiescent current - 60 mA. The amplifier has built-in thermal protection, as well as protection against overloads and short circuits in the load. The SA1 switch is used to "soft" turn on the amplifier. The device can be powered from a bipolar unstabilized source, the circuit of which is shown in fig. 2. The power of the network transformer is 250 V-A, the secondary windings must be rated for a current of at least 5 A.
Rice. 1. Scheme
Fig. 2
The parts of the amplifier are mounted on a printed circuit board (Fig. 3) made of double-sided foil fiberglass with dimensions of 50x35 mm; the assembled board is shown in fig. 4. Resistors MLT-0.25, capacitors C4-C7, SU - imported analogues K50-35 and K73-17 (the rest) were used for installation. As SA1, any small-sized push-button switch is applicable.
The loudspeaker head is broadband with an impedance of 4 ohms and a power of at least 50 watts. The microcircuit itself must be installed on a heat sink with an area of 600 cmXNUMX.
Fig. 3
Fig. 4
For better heat transfer, its body should be lubricated with a thin layer of heat-conducting paste. Since the microcircuit case is connected to the negative power wire, it must be isolated from the amplifier case.
Publication: cxem.net
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