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公开(公告)号：US4433254A
公开(公告)日：1984-02-21
申请号：US325207
申请日：1981-11-27
CPC分类号： H03G3/3005 , H03G7/002
摘要： A level detecting circuit for producing a level detected output signal in response to an input signal includes a logarithmic converting amplifier which logarithmically converts the input signal into a logarithmically converted signal; a differential error amplifier which produces a logarithmically amplified signal in response to the logarithmically converted signal and at least one feedback signal; an integrating capacitor supplied with the logarithmically amplified signal through a PN junction for producing an integrated signal; a voltage dividing circuit for voltage dividing the integrated signal and the logarithmically amplified signal in accordance with a selected ratio and supplying at least one resultant voltage divided signal as the at least one feedback signal to the differential error amplifier; and an output PN junction for producing the level detected output signal in response to the integrated signal.
摘要翻译： 用于响应于输入信号产生电平检测输出信号的电平检测电路包括对数转换放大器，其将输入信号对数转换成对数转换信号; 差分误差放大器，响应于对数转换的信号和至少一个反馈信号产生对数放大的信号; 通过PN结提供对数放大信号的积分电容器，用于产生积分信号; 分压电路，用于根据所选择的比率对积分信号和对数放大信号进行分压，并将至少一个合成的分压信号作为至少一个反馈信号提供给差分误差放大器; 以及输出PN结，用于响应于积分信号产生电平检测输出信号。
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公开(公告)号：US4441083A
公开(公告)日：1984-04-03
申请号：US300387
申请日：1981-09-08
CPC分类号： H03G9/025
摘要： A noise reduction circuit for use in an audio signal recording/reproducing apparatus is comprised of a first signal path including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and a differentiating circuit for differentiating at least that portion of the signal passing through the voltage-controlled amplifier within the audio range; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a feedback resistor connected as a negative feedback path with the first signal path for providing an upper limit to the gain imparted to the signal supplied to the noise reduction circuit; a subtraction circuit for subtracting the negatively fed back signals from the signal supplied to the noise reduction circuit to produce an input signal for the first signal path; a second resistor or a low-pass filter connected as a positive feedforward path between the input of the noise reduction circuit and the output of the first signal path for providing a lower limit to the gain imparted to the signal supplied to the noise reduction circuit; and an anti-limiting circuit connected in parallel with the feedback resistor for compensating the signal supplied to the noise reduction circuit when the level of the signal is abruptly increased.
摘要翻译： 用于音频信号记录/再现装置的降噪电路包括第一信号路径，该第一信号路径包括用于放大可控增益的供给的信号的电压控制放大器和用于至少区分信号通过部分的微分电路 通过音频范围内的压控放大器; 电平检测电路，用于响应于通过压控放大器的信号的电平来控制压控放大器的增益; 反馈电阻器，其作为负反馈路径连接到第一信号路径，用于提供施加到降噪电路的信号的增益的上限; 减法电路，用于从提供给所述噪声降低电路的信号中减去所述负反馈信号，以产生用于所述第一信号路径的输入信号; 连接在噪声降低电路的输入端和第一信号路径的输出端之间作为正前馈路径的第二电阻器或低通滤波器，用于提供给提供给降噪电路的信号的增益的下限; 以及与反馈电阻并联连接的反限制电路，用于当信号电平突然增加时补偿提供给降噪电路的信号。
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公开(公告)号：US4427950A
公开(公告)日：1984-01-24
申请号：US298099
申请日：1981-08-31
CPC分类号： H03G9/025
摘要： A noise reduction circuit for use in an audio signal recording/reproducing apparatus includes a first filter circuit for providing frequency emphasis to a signal supplied thereto; a first signal path connected in series with the first filter circuit, and including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and a second filter circuit for providing frequency emphasis to the signal passing through the voltage-controlled amplifier; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a resistor connected to the first signal path for reducing the effect of the frequency emphasis by the second filter circuit when the level of the signal passing through the voltage-controlled amplifier is reduced; and a low pass filter circuit connected with the first signal path for reducing the effect of the frequency emphasis by the first and second filter circuits when the level of the signal passing through the voltage-controlled amplifier is high; wherein the circuit for noise reduction provides a first amount of frequency emphasis for intermediate level signals supplied thereto and a second lower amount of frequency emphasis for low and high level signals supplied thereto. When used in its encoding mode, the first and second filter circuits each include a high-pass filter circuit, and when used in its decoding mode, these filter circuits each include a low-pass filter circuit.
摘要翻译： 用于音频信号记录/再现装置的降噪电路包括：第一滤波电路，用于向提供给它的信号提供频率强调; 与第一滤波器电路串联连接的第一信号路径，并且包括用于将可控增益放大到其中的信号进行放大的压控放大器和用于向通过压控放大器的信号提供频率加权的第二滤波电路; 电平检测电路，用于响应于通过压控放大器的信号的电平来控制压控放大器的增益; 连接到第一信号路径的电阻器，用于当通过压控放大器的信号的电平减小时，减小第二滤波器电路的频率强调的影响; 以及与所述第一信号路径连接的低通滤波器电路，用于当通过所述压控放大器的信号的电平高时，用于减小所述第一和第二滤波器电路的频率强调的影响; 其中用于噪声降低的电路为提供给它的中间电平信号提供第一数量的频率强调，并且向其提供的低电平和高电平信号提供第二较低的频率强度。 当在其编码模式下使用时，第一和第二滤波器电路各自包括高通滤波器电路，并且当在其解码模式下使用时，这些滤波器电路各自包括低通滤波器电路。
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公开(公告)号：US4453091A
公开(公告)日：1984-06-05
申请号：US360903
申请日：1982-03-23
CPC分类号： H03G1/0005 , H03G7/002
摘要： A level detecting circuit for use in a noise reduction circuit and which produces a level detected output signal in response to an input signal, includes an operational amplifier with at least one feedback diode for logarithmically converting the input signal to produce a logarithmically converted signal; a first PN junction element comprised of a first diode supplied with the logarithmically converted signal; a second PN junction element comprised of a second diode connected in series with the first diode at a connection point, the series-circuit of the first and second diodes having a first saturation current; a first integrating capacitor having a first capacitance and connected to the connection point for producing an integrated signal; a third PN junction element comprised of series-connected third and fourth diodes connected in parallel with the series connection of the first and second diodes and having a second saturation current greater than the first saturation current; a second integrating capacitor having a second capacitance less than the first capacitance and connected to the second and fourth diodes; a reference current source for providing a reference current to the series-connected first and second diodes and series-connected third and fourth diodes, and an output circuit for producing the level detected output signal in response to the integrated signal, such that, upon an abrupt attenuation of the input signal, the level of the level detected output signal is maintained for a predetermined time to substantially eliminate low frequency band harmonic distortion.
摘要翻译： 一种用于噪声降低电路并且响应于输入信号产生电平检测的输出信号的电平检测电路包括具有至少一个反馈二极管的运算放大器，用于对数转换输入信号以产生对数转换的信号; 第一PN结元件，由提供有对数转换信号的第一二极管组成; 第二PN结元件，包括在连接点处与所述第一二极管串联连接的第二二极管，所述第一和第二二极管的串联电路具有第一饱和电流; 第一积分电容器，具有第一电容并连接到所述连接点以产生积分信号; 第三PN结元件，包括与第一和第二二极管的串联连接并联的串联连接的第三和第二二极管，并具有大于第一饱和电流的第二饱和电流; 第二积分电容器，具有小于第一电容的第二电容并连接到第二和第四二极管; 用于向串联连接的第一和第二二极管和串联连接的第三和第四二极管提供参考电流的参考电流源，以及响应于积分信号产生电平检测的输出信号的输出电路， 输入信号的突然衰减，电平检测输出信号的电平保持预定时间，以基本上消除低频带谐波失真。
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公开(公告)号：US4441084A
公开(公告)日：1984-04-03
申请号：US300432
申请日：1981-09-08
CPC分类号： H03G9/025
摘要： A noise reduction circuit for use in an audio signal recording/reproducing apparatus is comprised of a first signal path including a voltage-controlled amplifier for amplifying a signal supplied thereto with controllable gain and integrating circuit for integrating at least that portion of the signal passing through the voltage-controlled amplifier within the audio range; a level detecting circuit for controlling the gain of the voltage-controlled amplifier in response to the level of the signal passing through the voltage-controlled amplifier; a feedforward resistor connected in parallel with the first signal path for providing a lower limit to the gain imparted to the signal supplied to the noise reduction circuit; an adder circuit for adding the output signals from the first signal path and the feedforward resistor; a second resistor or a low-pass filter connected as a negative feedback path between the output of the adder circuit and the input of the first signal path for providing an upper limit to the gain imparted to the signal supplied to the noise reduction circuit; and an anti-limiting circuit connected in parallel with the first signal path for compensating the signal supplied to the noise reduction circuit when the level of the signal is abruptly increased.
摘要翻译： 用于音频信号记录/再现装置的降噪电路包括一个第一信号路径，该第一信号路径包括用于放大其中提供的信号的可控增益的电压控制放大器和积分电路，用于至少整合通过的信号的那部分 音频范围内的压控放大器; 电平检测电路，用于响应于通过压控放大器的信号的电平来控制压控放大器的增益; 与第一信号路径并联连接的前馈电阻器，用于对被提供给降噪电路的信号赋予增益的下限; 加法电路，用于将来自第一信号路径和前馈电阻器的输出信号相加; 连接在加法器电路的输出端和第一信号路径的输入端之间作为负反馈路径的第二电阻器或低通滤波器，用于提供施加到提供给降噪电路的信号的增益的上限; 以及与第一信号路径并联连接的反限制电路，用于当信号电平突然增加时补偿提供给噪声降低电路的信号。
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