| 摘要 |
PURPOSE:To attain low cost by adopting the capacitor switch switching system to apply weighting by an input digital value at a time region thereby decreasing number of elements. CONSTITUTION:A switch S is driven a signal in a frequency (f), and when the switch S is changed over to the position of contact (a), a capacitor C is charged up into a voltage V1, and when the switch S is changed over to the position of contact (b), the capacitor is charged to a voltage (V2-VBE). An electric charge of Q=(V2-VBE-V1).C is injected to an emitter of a transistor (TR) and a current flows to a load resistor RL. Since the electric charge is given f-times per second, the average current I is Q.f(V2-VBE-V1).f.C and a voltage of V0=RL.I is generated. The circuit is connected as shown in the figure and a frequency driving each switch S is frequency-divided by flip-flops FFn-FF0, then binary weighting is applied. Collectors of TRs are connected in a way of wired-OR and the common load resistor RL is used, and an analog output is obtained at an output terminal of an LPF. |
