Amplifier with sixty DB dynamic range - despite high cutoff and precise logarithmic relationship of gain and control volts uses transistor differential pair

摘要

The amplifier has a dynamic range of 60dB despite its high cutoff frequency of greater than e.g. 10 MNz and despite having only a 0.1 dB variation in the logarithmic relationship between gain and control voltage. Two transistors are connected as a differential pair with the gain control voltage applied to one of their bases and the output signal taken from the other's collector. The input current (13) has a second current (14) added to it. This second current is proportional to the output current (12) and is added to the input current by a current reversing stage (T4, T5). A component proportional to the input voltage (Ue) is added to the control voltage (Us+).