| 摘要 |
<p>Signal expansion/compression apparatus wherein an input signal is compressed by an exponential factor and then subsequently may be expanded by the reciprocal of that exponential factor, wherein neither the signal compression circuits nor the signal expansion circuits need be provided with exponential amplifiers or logarithmic function generators. The signal compression circuit includes a plurality of serially-connected voltage controlled amplifiers, a first of such amplifiers receiving the input signal to be compressed and a predetermined one of such amplifiers providing the compressed output signal. A control signal generator is connected to the last of the voltage controlled amplifiers to produce a control voltage which is a function of the output signal of that last amplifier and a reference voltage. This control voltage is supplied to all of the voltage controlled amplifiers so as to determine the respective gains thereof. The signal expansion circuit includes a plurality of voltage controlled amplifiers, an input signal to be expanded being supplied in common to two of such amplifiers. An output of one of such amplifiers is combined with a reference signal to produce another control voltage which is supplied to all of the amplifiers in the signal expansion circuit so as to determine the respective gains thereof. The output signal produced by another amplifier is expanded with respect to the input signal. All of the voltage controlled amplifiers used in the compression and expansion circuits exhibit substantially linear gain characteristics and, preferably, are comprised of a voltage controlled impedance whose impedance value is linearly related to the applied control voltage.</p> |
