| 摘要 |
A circuitry arrangement for a resonant circuit that may be completely monolithically integrated and electrically tuned has a differential amplifier stage with two transistors T1, T1' fed by a constant current source I0 that are differentially loaded at their collectors by a voltage-dependent capacity and inductively loaded in relation to the circuit mass by a pair of emitter followers T2, T2' with electrically adjustable impedances that act upon the base. In order to implement the electrically adjustable impedances, transistors with associated resistances are provided (for example a pair of emitter followers T3, T3 with base pre-resistances R1, R1') which may be adjusted by control currents (for example I1, I1'). The voltage-dependent capacity is implemented by transistors T4, T4' whose short-circuited emitters and collectors are connected so that the circuit node thus obtained is applied to the circuit mass through a voltage source U1. This circuit arrangement may also be used in a controllable oscillator by interconnecting two resonant circuits in a loop. The output signal of the first resonant circuit is used to control the second resonant circuit and the output signal of the second resonant circuit is inverted and used to control the first resonant circuit. In this way, two signals may be tapped at the outputs of both resonant circuits. The frequency of said signals may be varied by a control voltage and their frequency-independent phase difference equals .pi./2. A particularly advantageous implementation of such an oscilla-tor is obtained by decoupling the output signals of both resonant circuits through two identical output driver stages. |
