| 摘要 |
<p>1,039,479. Transistor circuits. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Oct. 2, 1964 [Oct. 7, 1963], No. 40167/64. Heading H3T. In the transistor timer circuit shown the voltage at the emitter of transistor 12 is stabilized by connecting a non-linear element 15, such as a voltage dependent resistor, or a Zener diode, in parallel with the emitter-collector path and the relay load 14. The circuit is connected to a D.C. supply of high internal resistance and the capacitor 5 is charged by depressing pushbutton switch 4. The potential now at the junction between resistors 6 and 7 causes transistor 10 to conduct so that current flows from its emitter through the base-emitter circuit of transistor 12, which conducts to operate the relay. When the transistor cuts-off due to discharge of the capacitor 5 the current through resistor 13 is maintained by an increase in current through the non-linear element 15. In alternative circuits (Figs. 2 and 3, not shown), for use as a thermostat, an increase in temperature causes the current through the negative temperature coefficient resistor 7 to increase and so cause transistor 12 to conduct and operate the relay. The resistors 7 and 13 can be interchanged or can be replaced by positive temperature coefficient resistors. Variation in mains supply can be further compensated for by an additional non-linear element 19.</p> |
