A simplified version of the power amplifier circuit on complementary transistors. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
Comments on the article
It has the following main technical characteristics (see also Table 4):
Rated output power ...... 70 W
Harmonic distortion .......... 0,05%
Operating frequency band .......... 20... 80 Hz
Signal-to-noise ratio .......... 87 dB
Supply voltage .......... ±40 V
Quiescent current .......... 100 mA
The amplifier operates in AB mode and is made using the circuitry of the previous amplifier. The amplifier also has full symmetry for the input sinusoidal signal (the same input impedance for the positive and negative half-waves of the signal), which reduces the non-linear distortion.
Schematic diagram of the amplifier is shown in Fig.1. He contains
differential stage on complementary transistors (VT1-VT4), voltage amplification stage (VT5, VT7) and output stage (VT8-VT13). The supply voltage of the input stage is stabilized (using zener diodes VD1, VD2). The output stage transistors are connected in a common collector circuit. Temperature stabilization of the quiescent current of the output transistors is provided by VD3-VD5 diodes installed on a heat sink common with transistors VT12, VT13. Elements LI, R35, R36, C11, R20, C7 prevent self-excitation of the amplifier at high frequencies.
Fig.1 (click to enlarge)
Diodes VD3 - VD5 are placed on the radiator of the output transistors. Coil L1 contains 10 turns of PEV-2 0,8 wire wound on a resistor R35 (MLT-2).
As in the previous amplifier, first you need to check the health of all elements. After installation (checking its correctness), the amplifier, similarly to the previous one, is connected to a power source. The setting consists in setting the initial current of the output transistors with resistor R29 within 50 ... 70 mA.
The amplitude 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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