| 摘要 |
<p>1532658 Transistor gating circuits, pulse amplitude modulators NIPPON HOSO KYOKAI 28 Nov 1975 [29 Nov 1974] 48914/75 Headings H3T H3H and H4L In a differential charge coupled amplifier, charge is transferred between two capacitors C2, Cl in dependance on clock signals Al, A2, A3 so that an output signal is produced which corresponds to the difference between two input signals B and E applied to the emitter and base respectively of a transistor Tr 1 . During a first clock interval, points A1, A2 are at a high level, so that diode D2 turns on to allow capacitor C1 to charge to the difference between the clock voltage at A1 and the sampled and stored value at B of the first analogue input signal. Point A3 is also at a high level, so that capacitor C2 charges to the clock voltage. During the next clock interval points A1, A2, A3 are at low clock level turning on transistor Tr 1 . Capacitor C2 now discharges into capacitor C1 until the voltage across it is equal to the difference between the second analogue input E and the value stored on C1 during the previous clock interval. In modifications, the diode D1 may be replaced by a transistor circuit similar to Tr 2 , d1, cl associated with the first capacitor, Fig. 5 (not shown) or the transistor circuit Tr 2 , dl, cl may be replaced with a diode (D3) Fig. 6 (not shown). The diode D2 may be replaced by an equivalent circuit having zero impedance Fig. 7 (not shown). The charge coupled circuit is used in an A/D converter in which higher order levels of the input analogue signal are A to D converted at 12 to provide the upper bits of the digital signal and reconverted back to analogue form at 13 to provide the second input E to the charge coupled circuit 10, the sampled input signal providing the first input B. The output of circuit 10 is then converted in a second A to D converter 14 to provide the lower bits of the digital output.</p> |
