| 摘要 |
<p>An electronic circuit for imitating a capacitor with a controllable capacitance comprises a chain (CHN) of at least two differential pairs (DF1-DF3), the tail of each differential pair (DF1-DF3) being connected to a reference terminal (GND) via a respective separate current source (I1-I3). Each differential pair comprises a first and a second input. All the first inputs of the differential pairs (DF1-DF3) are connected to a signal terminal (CPVR) of the electronic unit. All the second inputs of the differential pairs (DF1-DF3) are interconnected via means (SPMNS) for supplying separate DC voltages between the second inputs of the differential pairs (DF1-DF3). Between the signal terminal (CPVR) and the reference terminal (GND) a capacitance is formed which is the sum of the input capacitances of the differential pairs (DF1-DF3). The capacitance is determined by the amount of charge per unit of voltage which is delivered to the first inputs of the differential pairs (DF1-DF3). If the separate DC voltages between the second inputs of the differential pairs (DF1-DF3) increase, then said amount of charge will decrease and as a consequence the capacitance will decrease. Thus the capacitance can be varied in that said separate DC voltages are varied.</p> |
