| 摘要 |
A power control circuit (10) contains a voltage controlled attenuator (16) in combination with a logarithmic converter (24) to produce linear amplification of an input signal (12) over as wide a frequency output range as possible. A logarithmic converter for use in such a power control circuit is provided, comprising amplifying means (60) with a non-inverting (66) and inverting (70) input and an output (64), and two feedback means (62, 68). The feedback means are separably connected between the output and an input of the amplifying means, so that the first feedback means (62) produces a feedback signal which results in the amplifying means (60) exhibiting a non-linear characteristic and the second feedback means (68) contains at least one reactive element (108) to limit the feedback signal from the first feedback means (62) above certain signal levels. The first feedback means may be provided by emitter coupled transistors (76, 78) or two Darlington transistor pairs. The second feedback means is zener diode (108). |
