| 摘要 |
Analog signals within an amplitude range of +/- 2Uref (Uref being a fixed reference potential) are classified by a decision network as falling within one of 2m positive or negative amplitude bands progressively increasing in width by a factor of 2, the identity of the band being registered by a precoder generating m bits to which is added a further bit indicating the polarity of the signal. An amplitude converter passes each signal to a final coder, with an amplification factor depending upon the particular amplitude band as determined by the decision network. At least a final stage of the amplitude converter works directly into the final coder and includes one or more operational amplifiers each with an additive and a subtractive input, the latter being connected to the amplifier output through a feedback circuit which comprises a voltage divider determining the amplification factor and a source of biasing voltage of magnitude 2Uref for generating a zero output at the lower limit of each band. For the lowest band, ranging between O and Uref/2(2 <->2), the biasing voltage is cut off. The amplifier output is digitized in the final coder to yield n more bits for a total of 2n<+>m<+>1 discrete amplitude values.
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