| 摘要 |
Circuit for reducing noise in an amplifier (4). The signal is fed to a preamplifier (1) whose output is connected to a variable resistance which contains two diodes (19, 20). The diodes are used to attenuate the input signal when its amplitude is below a predetermined level. Above this level the signal is transmitted and rectified. The diodes are connected in series and the signal is fed to the junction point which is also the input terminal to the amplifier (4). When the input signal is below the threshold level a network (2, 3) will bias the diodes in the forward direction so that they will act as a shunt for the incoming signal. The rectifier circuit (15, 16) has a network (17, 18) connected in parallel with the two diodes which acts as a memory, adjusting their bias when the signal is to be transmitted. |
