| 摘要 |
937,541. Transistor switching circuits. COLLINS RADIO CO. July 20, 1961 [Jan. 3, 1961], No. 26373/61. Class 40 (6). A circuit for monitoring the magnitude of a direct voltage and connecting the voltage to earth if it exceeds a predetermined value comprises an input emitter-follower transistor 7, the output from which is applied to a unijunction transistor 19 which conducts when the input voltage exceeds said predetermined value, the voltage pulse developed as a consequence across load resistor 21 switching normally conducting transistor 11 off, thus removing collector bias from transistor 7 so that its collector-base diode becomes forwardly conducting and the input voltage is earthed through resistor 15. By virtue of the long time-constant circuit comprising resistor 32 and capacitor 34, transistor 11 remains cut off for about half a second after each pulse from the unijunction transistor. At the end of this period, if the excess voltage has been removed, the circuit returns to its original state. The input voltage may be a frequency control voltage for an oscillator as described in Specification 937,542. |
