Three-band UMZCH on microcircuits. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transistor power amplifiers
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A three-band audio frequency power amplifier, the circuit of which is shown in the figure, provides a rated output power in the low-frequency channel of 30 W at a load of 4 ohms, in the mid-frequency and high-frequency channels - 15 W each at a load of 8 ohms.
Resistors R3 - R6, capacitors C2 and C3 and the DA1 chip form an active low-pass filter with a cutoff frequency of 300 Hz. Elements R10 - R15, C10-C13, together with DA2 - a bandpass filter 300 ... 3000 Hz, and R19 - R22, C19 - C21 and DA3 - a high-pass filter with a cutoff frequency of 3000 Hz. The steepness of the slopes of the filters from 12 to 18 dB per octave.
The gain of the LF channel is 34, the MF and HF channels - 23.
Circuits R9C8, R16C16, R23C23 are used for the stable operation of amplifier microcircuits DA1 - DA3, diodes VD1 - VD6 protect microcircuits from inductive surges on loads.
The R17R18 divider provides half the supply voltage at the non-inverting inputs of the DA1 - DA3 microcircuits.
The closest domestic analogue of the applied TDA2030A microcircuits are KR174UN19A. Transistors BD908 and BD907 can be replaced by transistors of the KT864 and KT865 series, respectively (with the same letter indices in a pair); instead of 1N4001 diodes, KD243 with any letter index is suitable, as well as any others for a working current of at least 1 A and a voltage of at least 50
Author: V.N.Schreiber
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