| 摘要 |
<p>1,038,416. Transistor amplifiers; tuning control. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. April 24, 1964 [April 27, 1963], No. 17085/64. Headings H3Q and H3T. [Also in Division H2] The tuning member 12 of a radio receiver is driven through reduction gear 11 by D.C. motor M having constant field excitation and its armature connected in an output circuit of a difference amplifier comprising transistors T1-T4, the input terminals E1, E2, of the amplifier receiving an error voltage (e.g. the difference between the voltages of two potentiometer tappings) which represents the displacement of the timing member from a desired stopping- position. The armature of the motor may be shunted by a damping resistor formed by transistor T5. As the stopping-position is approached, the current passing through resistor R9 is reduced so that transistor T5 is rendered conductive for braking the motor and preventing over-run. Deviation from a stopping- position causes a voltage to be developed across resistor R9 whereby transistor T5 becomes non- conductive to remove the braking-effect. When the motor is driven in the opposite direction. it passes through the stopping-position and is not braked until it has reversed its direction of rotation.</p> |
