CONTROLLED HYSTERESIS INTEGRATED CIRCUIT SWITCHING CIRCUITS

摘要

1313917 Transistor switching circuits LANDIS & GYR AG 8 Sept 1970 [16 Sept 1969] 42967/70 Heading H3T An integrated bi-stable includes an amplifier 9, a current Is source 12 and means such as T19 responsive to the sign of the amplifier output to switch the source 24 in circuit with the amplifier input by way of R14, R15 to produce current. flow I H (from R21) through R15 in opposition to I S , and thereby to establish hysteresis. An input voltage U G is applied across the inputs of amplifier 9 and a threshold voltage is also applied by virtue of current flow through R15 from a constant current source 12 to a Zener diode 16, the latter also drawing current from a resistor R21. Starting from a condition where T19 of an emitter-coupled pair T19, T20 is held off and T20 on by the amplifier output, the input U G goes negative until T19 is turned on, its collector current flowing from R21 through R15, R14 in opposition to the threshold setting current. This enhances the switching of amplifier 9 and of T19, T20 to the opposite state. Also, the voltage drop across R15 having been removed or reversed, the change required in U G to reset the circuit involves a hysteresis which is adjustable by varying the current I H from 24 A switching circuit 26 is driven by amplifier 9 and controls a relay 29, and also provides feedback through a time delay circuit 30 to the input of amplifier 9. A second, similar bi-stable using an amplifier 8, T17, T18 and a switching circuit 25 has its threshold controlled by R14 and a current source 23 for T17, T18, thus providing a two-threshold circuit responsive to an input passing outside these threshold levels.