| 摘要 |
1,247,702. Bipolar discriminator. MOTOROLA Inc. 29 Oct., 1968 [30 Nov., 1967], No. 51260/68. Heading H3T. ' A strobed discriminator 36 receives bipolar signals, for example from a differential amplifier 34, and provides a single polarity output 6, and consists of input transistors 10, 12 driving further transistors 14, 16 respectively which are also connected to the opposite driving transistors 12, 10 such as by connecting their emitters, and whose outputs are connected together at the output 6. Each input transistor 10, 12 has its emitter connected through a respective gating transistor 18, 20 and through a common resistor 24 to supply -V3, a strobe pulse at 7 rendering the transistors 18, 20 conductive. The transistors 14, 16 have a common collector resistor 21 so that when one or the other conducts according to the polarity of the differential amplifier output, the voltage at 6 falls. This fall is transmitted through a diode-connected transistor 78 and a capacitor connected transistor 80 to the base of a normally conducting transistor 88 to turn it off and increase the current flow in a transistor 94. A doublediode-connected transistor 84 having two emitters prevents transistor 88 from saturating. The transistor 94 drives an emitter follower 102 having another double-diode-connected transistor 98 to clamp the positive limit of its base voltage to earth; the output 40 being consequently - VEB, the emitter-base drop of transistor 102. The negative limit of the output, existing when the transistor 88 is normally on, is defined by the approximatley Earth potential on transistor 94 emitter (its base being VEB above E on account of the double diode 84 and the emitter-base function of transistor 88), and by the voltage drop across diode 98 and the emitter-base function of transistor 102, so giving an output of - 2V EB . The output thus swings between about - 0.8 V and - 1-6 V in response to the input at 31. A voltage supply circuit 71 includes an emitter follower 68, and a pair of temperature compensating diode-connected transistors 64, 66; the differential amplifier 34 also includes a temperature compensating diode 56 |
