LM1894 Principles and Applications a


Posted on Mar 28, 2007

A typical representative of the dynamic noise reduction by the United States National Semiconductor first be successfully developed and integrated LM1894 (see Table 1-3), the u


LM1894 Principles and Applications a
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pper part of the figure 1-1070 its principle is shown in the left and right the same two a main signal path, the left and right input signals respectively, by 132 feet and after the noise reduction processing is output from 11,4 foot. Between the input and output, A2 constituted by the variable gain OdB and band-pass cut-channel control of the low-pass filter o the lower part of the figure as Vice signal control channel, a shared control channel around here, it will help simplify the circuit. First in the left and right input signals are mixed into the adder A3 all the way, and then the deputy - amplification and signal amplifier As, VD group after a peak detector detector 10 feet to get a DC control voltage, and then by the built-in voltage/current (V /,) converter into a DC control current to Ai to change the main channel bandwidth. Press the noise reduction design requirements, the input signal frequency component richer, the greater the DC control voltage is converted into a DC control current is smaller, the corresponding main channel bandwidth wider. Specifically, the control current is decreased by 1 per belly to increase bandwidth 27Hz. Conversely, when the input signal into a high frequency, the less points, the narrower the bandwidth of the main channel, typically 800Hz ~ 1,1 seven o




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