DC current negative feedback OCL circuit application 
According to the "Electronic Report" 2001 "LNl875 power amplifier production experience" a circuit (Figure 1) experiment, the results are indeed as described in the article, after the circuit is DC and changed to current feedback, the frequency response is widened, the bass speed Obviously enhanced, the high-frequency resolution increases, the mid-range texture is enhanced, the sound quality is much higher than the standard circuit, so that it can be listened to for a long time. Use this power amplifier to compare with the new Dirk 6800 pure class A power amplifier, and push the Swans M1.2 speaker. 15 square meters of room, about 10W output, the sound is very close to the new Dirk machine, sound power, resolution is comparable. LMl875 high-pitched and fine, Xindeke 6800 vocal thickness is strong - point, the difference between the two is small, unexpected.
However, the lack of LLM875 DC current negative feedback circuit also makes people feel that if it is lost: the power is too small, there is audible hum sound when static, when the measured LMl875 static output has several to ten mV voltage.
This article refers to the address: http://
LMl875 DC current negative feedback BTL design LM1875 application circuit
The DC current negative feedback BTL circuit is shown in Figure 2. The C12 and C22 in the standard BTL circuit are canceled to make the circuit DC. The resistors R16 and R26 are the sampling resistors. The current feedback signals enter the amplifier A1 through R15, R16, R25 and R26 respectively. The inverting input of A2, the resistance of R13, R14, R15, R16 determines the size of the amplifier gain.
Using the circuit experiment of Figure 2, no matter how the power and input signals are turned on and off, there is no DC output at the output end, and there is no static output noise. There is only a slight “beep†sound in the speaker when the power is turned on, and there is no noise in the speaker when the power is turned off. It can be seen from experiments that the input circuit works very stably. Even if the input terminal is unplugged and plugged in when the volume is turned on or static, the circuit will not be self-excited. Capacitor C11 has a great influence on the sound quality. After removing this capacitor, the front is bright, the middle and high notes become clear and delicate, and the bass is flexible and strong. The DC current negative feedback BTL circuit inherits the advantages of the DCN current negative feedback OCL circuit sound quality, the distortion is further reduced, the output power is increased to 3 times, reaching 60 watts or more, overcoming the impact of the switch machine speaker. The shortcoming of humming sound in both sound and static is the ideal optimization circuit for the LM1875.
E-cigarette
Shenzhen Yingyuan Technology Co.,ltd , https://www.smartpuffvape.com