Bridged power amplifier. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
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It has an output power of 60 W with a single +40 V power supply. Getting a large output power is associated with a number of difficulties, one of which is the limitation of the power supply voltage, due to the fact that the range of high-voltage power transistors is still quite small. One of the ways to increase the output power is the series-parallel connection of the same type of transistors, but this complicates the design of the amplifier and its tuning. Meanwhile, there is a way to increase the output power, avoiding the use of hard-to-reach elements and not increasing the voltage of the power supply. This method consists in using two identical power amplifiers connected so that the input signal is applied to their inputs in antiphase, and the load is connected directly between the outputs of the amplifiers (amplifier bridge circuit).
A power amplifier made according to such a bridge circuit has the following main technical characteristics:
Rated output power ...... 60 W
Harmonic distortion .......... 0,5%
Operating frequency band .......... 10... 25 Hz
Supply voltage ........... 40 V
Quiescent current .......... 50 mA
A schematic diagram of such an amplifier is shown in Fig. 1. Changing the phase of the input signal is achieved by applying it to the inverting input of one and the non-inverting input of another amplifier. The load is connected directly between the outputs of the amplifiers. To ensure temperature stabilization of the quiescent current of the output transistors, diodes VD1-VD4 are placed on a common heat sink with them.
Ris.1
Before turning on, check the correct installation and connections of the amplifier. After connecting the power supply with resistor R14, a voltage of no more than 0,5 V is set between the outputs of the amplifier. The amplitude-frequency and phase-frequency characteristics of the adjusted amplifier are shown in Fig. 2.
Ris.2
Literature
- D.I. Ataev, V.A. Bolotnikov. Practical schemes for high-quality sound reproduction. M. Radio and communication. 1986
Publication: N. Bolshakov, rf.atnn.ru
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