| 摘要 |
1,209,116. Television. ALBISWERK ZURICH A.-G. 15 May, 1968 [15 June, 1967], No. 23015/68. Heading H4F. In a television circuit arrangement for stabilizing the black level of a video signal, supplied from terminal E via an A.C. coupling 3, by means of a diode 4 and a reference potential UB, the anode of the diode is connected to the emitter of a first transistor 1 connected in an emitter followed configuration and having its base connected to the reference potential via a second diode 5 and the video signal supplied to the cathode of diode 4 is fed to the cathode-ray display tube 7 via a complementary transistor 2 and a D.C. coupled amplifier 9. With this arrangement the difference UD between the output reference potential A and the reference potential UB (derived from the common connection point of two identical D.C. voltage sources U1, U2) is equal to UBE2+U4 - UBE1 - U5, where UBE1 and UBE2 are the base emitters voltages of transistors 1 and 2 respectively and U4 and U5 are the forward voltages of diodes D4 and D5 respectively. Since the base emitter voltages of the transistors are of equal magnitude and likewise the forward voltage of the diodes, UD is therefore equal to zero and changes in the forward voltage of the diode 4 due to temperature effects are self compensating. When several of the circuits described are to be used simultaneously in different channels in the same device that portion of the circuit including transistor 1 may be common to all the channels. |
