| 摘要 |
A television camera including a preamplifier suitable for use with a pick-up tube (1) comprising an anti-comet tail gun (ACT). A preamplifier input terminal (9) which is connected to the pick-up tube (1) by a direct current connection (10) is connected to a control electrode (8) of a transistor (12), to a terminal (13) of a resistor (14) and, in accordance with the invention, by a diode (24) to a terminal (26) carrying a reference voltage. The diode (24) is non-conductive during line scanning periods (THS) and conductive during that period (THB1) of line blanking periods (THB) in which current peaks produced by the anti-comet tail gun (ACT) occur. The diode (24) has a low capacitance (C29), for example, less than 1 pF and a low threshold voltage and anode-cathode voltage drop (Vd) of the order of magnitude of some tenths of volts. A Schottky-barrier diode may be used as the diode (24). The diode (24) ensures that the preamplifier is not saturated for an impermissbly long period of time at the limit of its operating range due to the current peaks.
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