| 摘要 |
<p>1,110,552. Analogue-to-digital converters. STANDARD TELEPHONES & CABLES Ltd. 18 March, 1966 [22 March, 1965], No. 11963/65. Heading G4H. [Also in Division H3] In an analogue-to-digital converter of the kind described in Specification 1,046,792 in which the input signal having a damped oscillation superimposed upon it is applied to a group of series-connected bi-stable threshold devices which switch in succession and subtract a weighted signal the characteristic of the bi-stable elements is modified so as to have a portion BC, Fig. 2, of flatter slope. This improves the operating characteristics. In the form of Fig. 3A, for quantizing a current, generator G produces the input signal and damped oscillation, Fig. 3B. Bi-stable elements D1, D2, D3, D4 are connected in series with a resistor RO and generator G. The elements D1-D4 may be PNPN devices. Their characteristics, Fig. 4, are all the same but differ by a scale factor of 2 between each and the next. The characteristics are modified as indicated by the dotted line by circuits VS1- VS4. These each comprise a diode (D10, Fig. 5, not shown) biased by a source (E1) so as to conduct from 0-i2, Fig. 4, and from i2 to i3 to cut off so that a resistor (Rl) is inserted. At i3 a Zener diode (ZD) starts conducting in series with a diode (D11) biassed by another source (E2) to conduct until point i4, when it cuts off.. The characteristic is therefore steep when (D10) stops conducting, shallow when the Zener diode and diode (D11) conduct and steep again when this diode cuts off.</p> |
