Suitable for self-made integrated circuit power amplifiers

4

The power amplifier circuit schematic diagram consists of three parts: power amplifier, power supply and switch protection.
    The power amplifier part is composed of four LM1875s . Each channel uses two LM1875s to form a BTL amplifier. The output power
is not less than 2×70W, which is enough to meet the requirements of home playback. The circuit adopts the BTL standard
circuit recommended by National Semiconductor. There are now articles suggesting the use of servo DC technology in the LM1875 power amplifier. This article believes that the performance improvement is limited and greatly
increases the complexity of the circuit. It is not suitable for enthusiasts to make their own products, so it is not used in this power amplifier. Just
add a 200pF capacitor at the input end of the power amplifier to form a low-pass filter
to remove some super audio signals mixed into the audio signal
. This can reduce the transients of the amplifier at high volumes
. ． White: Adjust distortion to make the sound better.
    The power supply part adopts the form of traditional transformer step-down and diode
rectification. The transformer capacity is required to be no less than
200W, otherwise it will affect the sound playback intensity. If possible, it
is better to have a larger capacity as much as possible. 6. The filter circuit
uses a combination of inductors and capacitors. P, that is, R (half-wave) type
filter. This filter is mostly used in professional instruments and
has better performance than simple capacitor filtering. Please note
that the DC output voltage after filtering is approximately 0.0% of the AC input
voltage . 98 times. The inductor L needs to be homemade. The method is to use
a power transformer core of about 10W and wrap it with about
4rl. 2mm enameled wire. It is best to dip the inductor into paint to reduce the noise.