First, the chip description
TDA7294 is a well-known DMOS high-powered successful discharge circuit from the famous SGS-THOMSON Italian microelectronics company introduced to mainland China in the 1990s. It sweeps away the raw, cold and hard sounds of the previous linear set and the thick film integration, and is widely used in the HI-FI field: home theater, active speakers, etc. Tda7294.pdf
The chip's design focuses on timbre and combines the advantages of bipolar signal processing circuitry and power MOS. It has the characteristics of high voltage resistance, low noise, low distortion, and reproducible sound. It also has a silent standby function, short-circuit current and overheat protection to make its performance more perfect. The relevant electrical parameters are as follows.
Operating voltage range: (VCC + VEE) = 80V
Output power: up to 100W
Voltage range: |VCC|+|VEE|=20V-80V
Static current: 30MA
Output power: |VCC|=|VEE|=35V, 70W when RL=8 ohms
Total harmonic distortion (THD): 0.01% (typical)
Conversion rate (SR): 10V/us
Open loop gain: 80dB
The unit price of the author is 13 yuan; due to the limitations of the conditions, the author test circuit is soldered with a universal board, as long as the speaker is not too difficult sound quality is not bad; because the author's technology is not yet mature, to better play the sound of this chip, please master Pointing improvement.
Second, the pin data <br> Each end of the role is as follows:
1 pin is the standby end; 2 pin is the inverting input terminal;
3 feet are the positive phase input; 4 feet are grounded;
5, 11, 12 feet are empty feet; 6 feet are bootstrap end;
7 feet are +Vs (signal processing part); 8 feet are -Vs (signal processing part);
9 feet are standby feet; 10 feet are silent feet;
13 feet are +Vs (last stage); 14 feet are output ends;
15 feet are -Vs (last level). 
Third, the circuit diagram description 1. R1, R2 and R5 form a typical power amplifier with a magnification of approximately 32 times R5/R1;
2. C1, C2, C8, and C9 are power supply filter capacitors;
3.9 feet and 10 feet can be additionally switched to control standby and mute, C6, C7 as filtering and debounce. 
Fourth, the test conditions 1, no load, with WD-5 regulator source +12.1 -12.1 +5.0 to provide power and allowable bits.
2. Use SG1732SB5A DC stabilized current supply as input.
3. Measure the value with the multimeter SYG DT9205G. 
V. Test Summary <br> Start testing mistakenly believes that the linear range is low. After analysis, only the amplification factor is too large, but the maximum voltage of 3.86V is still too small for some high-voltage output requirements; it is good as a general-purpose audio chip (excluding fever) Category).
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