| 摘要 |
<p>807,387. Direct-coupled amplifiers. ATOMIC ENERGY OF CANADA Ltd. Jan. 7, 1957 [Jan. 31, 1956], No. 601/57. Class 40 (6). An amplifier for measuring small currents over a wide range and unaffected by voltage variations or ageing of tubes comprises two similar feedback amplifiers each having at least two direct-coupled stages V2A, V3A and V2B, V3B. In each amplifier a feedback is provided from the cathode of the output stage to the grid of the input stage which includes a diode rectifier V1A, V1B and the output is taken between the cathodes of the output stages. In this way the input signal current is translated into logarithmic variations of voltage by the diode rectifier in the control grid circuit. The diode rectifiers may be electron tube rectifiers in a common envelope. Potentiometers P1A, P2B are provided to adjust the gain. With zero signal in diode VIA the point 10 may be set to earth potential and also point 11 by potentiometer P2B. The input tubes V2A, V2B are preferably electrometer tubes fed from a stabilized filament supply. The cathode heater supply of the diode rectifiers V1A, V1B is also preferably stabilized. Positions 2 and 3 of switches S1A, S1B are for setting and calibrating. A reference signal may be applied to the second amplifier, for example when used with a photometer the light source may affect a photosensitive device to provide a voltage as a reference signal to compensate light intensity variations of the source.</p> |
