Test and Application of Power Amplifier TDA7294

1. Chip Description

TDA7294 is a rather innovative DMOS high-power integrated amplifier circuit introduced to mainland China by the famous European SGS-THOMSON STMicroelectronics in the 1990s. It swept away the raw, cold and hard sound of previous linear integrated amplifiers and thick film integration, and is widely used in the HI-FI field: such as home theaters, active speakers, etc.

The design of this chip focuses on the sound quality, and has the advantages of bipolar signal processing circuit and power MOS. It has the characteristics of high voltage resistance, low noise, low distortion, and extremely friendly playback sound quality; and it has a silent standby function, short-circuit current and overheating protection functions to make its performance more perfect. The relevant electrical parameters are as follows.

Operating voltage range: (VCC+VEE) = 80VOutput
power: up to 100WVoltage
range: |VCC|+|VEE|=20V-80VQuidity
current: 30MAOutput
power: |VCC|=|VEE|=35V, 70W when RL=8 ohmsTotal
harmonic distortion (THD): 0.01% (typical value)
Slew rate (SR): 10V/usOpen
loop gain: 80dB

The unit price where I live is 13 yuan. Due to limited conditions, I tested the circuit with a universal board for soldering. As long as the speaker is not too difficult, the sound quality is good. As my technology is not yet mature, I would like to ask experts for advice on how to improve the sound effects of this chip.

2. Pin information
The functions of each pin are as follows:
　　Pin 1 is the standby terminal; Pin 2 is the inverting input terminal;
　　Pin 3 is the non-inverting input terminal; Pin 4 is grounded;
　　Pins 5, 11, and 12 are empty pins; Pin 6 is the bootstrap terminal;
　　Pin 7 is +Vs (signal processing part); Pin 8 is -Vs (signal processing part);
　　Pin 9 is the standby pin; Pin 10 is the mute pin;
　　Pin 13 is +Vs (final stage); Pin 14 is the output terminal;
　　Pin 15 is -Vs (final stage).

3. Circuit diagram description
　　1. R1, R2, and R5 form a typical power amplifier with an amplification factor of about 32 times that of R5/R1;
　　2. C1, C2, C8, and C9 are power filter capacitors;
　　3. Pins 9 and 10 can be equipped with switches to control standby and mute, and C6 and C7 are used for filtering and de-jittering.

IV. Test conditions
　　1. No load, use WD-5 voltage regulator +12.1 -12.1 +5.0 to provide power and enable bit.
　　2. Use SG1732SB5A DC voltage and current regulator as input.
　　3. Use multimeter SYG DT9205G to measure the value.

V. Test summary
　　At the beginning of the test, it was mistakenly thought that the linear range was low. After analysis, it was just that the amplification factor was too large, but the maximum voltage of 3.86V is still too small to meet some high voltage output requirements; as a general audio chip, it is still good (excluding fever).