The famous European SGS-Thomson STMicroelectronics has launched a Hi-Fi high-power DMOS set with better timbre and higher power than TDA 7294-TDA 7293. It is basically the same as the internal structure of TDA72294, and is divided into three stages: the differential input stage is composed of bipolar transistors, the driving stage and the power output stage use field effect transistors, which have low distortion, low noise, and high withstand voltage (higher than TDA72294 ± 10V) and the advantages of on / off mute, overheat protection, short circuit protection, etc.
TDA72293 is a 15-pin package. The function of each pin is not completely the same as that of TDA72294. The function of each pin is as follows: {1} pin is the standby ground; {2} pin is the inverting input terminal; {3} pin is the positive-phase input terminal; {4} Pin is the ground; {5} Pin is the CLIPDET; {6} Pin is the bootstrap end; {7} Pin is + V (signal processing part); {8} Pin is -V (signal processing part); {9 } Pin is the standby terminal; {10} pin is the mute terminal; {11} pin is the BUFFER DIVER; {12} pin is BOOT LOADER; {13} pin is + V (power output stage part); {14} pin is the power output End; {15} foot is -V (power output stage part).
The main parameters of TDA72293: 1. Operating voltage range: ± 12V ~ ± 50V; 2. Peak output current 10A; 3. Output power: 100W at ± 40V, 8Ω; 140W at ± 45V, 8Ω; 100W at ± 29V, 4Ω; 4. Total harmonic distortion (P0 = 5W, f = 1kHz) 0.005%; 5. Conversion rate is 15V / μs (TDA72294 is 10V / μs). 6. Input impedance 100kΩ; 7. Frequency response 20Hz ~ 20kHz? 8. Work in Class A and B.
In order to play the ultimate effect of TDA72293, I designed TDA7293 as a current negative feedback constant current power amplifier (with DC servo) and designed as a two-channel protection circuit with speakers. In order to prevent the interference of alternating current on the signal, the author adopts the split design of power supply and power amplifier board. The power supply uses double-bridge rectification (two 10A bridge stacks), and the filter uses four 10000μF plus two 0.1μF capacitors.
The power amplifiers on the market no matter how much voltage type negative feedback is used for Class A and Class A and Class B. The output voltage of the voltage-type negative feedback power amplifier is only related to the amplification factor, but not to the impedance of the speaker, which makes the amplifier unable to overcome both nonlinear distortion and transient distortion. The use of current negative feedback can solve this shortcoming: the linear component resistance is used to feed back the current flowing through the speaker voice coil to the power amplifier input terminal, so that the amplifier drives the load with a fixed current, and the speaker can sound well under the current control oscillation. Solve the problem that the nonlinear distortion and transient distortion in the power amplifier cannot be taken into consideration.
The above figure is the circuit schematic diagram of the current negative feedback constant current power amplifier using TDA72293 (only one channel is drawn in the figure, and the other channel is the same). Using current negative feedback, it also includes the speaker system in the feedback network, plays a positive role in controlling the speaker, and effectively cancels the distortion caused by the speaker vibration.
In order to solve the digital music source (such as CD, VCD, DVD, etc.) digital music is hard and hairy, this circuit has a softening effect on digital sound, which can soften the forward hair "hair" sound of the digital sound source and soften the dryness The sound softening function of this function is the cf1 high-frequency AC gain compensation network in the figure. Its function is to attenuate digital sound (compress or attenuate high-frequency overtones of 60 to 80 kHz or higher). The IC2 in the figure acts as a DC servo.
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