| 摘要 |
1. Visual indicator of the variation sense of a variable direct voltage, particularly the tuning voltage applied to the variable capacity diodes used in the resonance circuits of the high frequency stage (tuner) of a heterodyne receiver, characterized by the fact that it comprises an electronic circuit (10) comprising a differential amplifier (11) provided with two transistors (110, 111) coupled on their emitters to one (6) of the supply terminals of the circuit (10) through a first common resistor (113) and the collectors of which are respectively connected to another (5) supply terminal of the circuit (10) through two resistors (116, 117) of the same value, the base of the first transistor (110) being directly connected to an output (2) delivering said variable direct voltage, whereas the base of the second transistor (111) is connected to said output (2) through a second resistor (114) and to the other supply terminal (5) through a capacitor (115) together forming an integrating circuit delaying application of the variation of the variable voltage to said base, the differential amplifier (11) being further provided, in the circuit of the first transistor (110), with a balance resistor (112) compensating the voltage drop produced by the base current of the second transistor (111) between the terminals of the second resistor (114), so that, with the exception of the variation periods of said voltage or those following these variations, the respective emitter-base voltages of the two transistors (110, 111) are substantially equal, the collectors of the two transistors (110, 111) being respectively coupled with two light signalling devices (18, 19) the lighting of which by a voltage applied to their terminals indicates positive and negative variations, respectively, of the variable direct voltage exceeding a predetermined level in modulus. |
