| 摘要 |
<p>1,154,898. Crystal oscillator circuits. STANDARD TELEPHONES & CABLES Ltd. 30 Nov., 1967, No. 54587/67. Heading H3T. Temperature compensation for a crystal oscillator is-provided by means of a compensating variable reactance controlled by the base to emitter voltage of a transistor. Varactor diode VD1 is connected in series with the oscillating crystal and has one of its electrodes fixed-biased from a potentiometer, comprising resistors R5, R6. The other electrode of diode VD1 is biased via resistor R7 from the collector circuit of a transistor VT1 which is provided with an emitter bias resistor R4, the base being biased from potentiometer R1, R2. The resistors R5, R6 may be replaced by a variable potentiometer, the slider of which provides bias to the electrode of diode VD1, or this electrode may be biased directly from the H.T. supply line via a resistor of high value. Resistors R1, R2 provide base bias for the transistor, but may be replaced by an adjustable potentiometer.</p> |
