| 摘要 |
<p>MULTIPLEXING SWITCH WITH WIDE BANDPASS CHARACTERISTICS AND HIGH ISOLATION IMPEDANCE BETWEEN INPUTS The multiple-input, common-output switch disclosed herein has a wide bandpass characteristic of approximately 0 to 90 Megahertz and is thus capable of passing most any digital or analog signal. At the same time, high isolation is maintained between each of the inputs and the common output so that many inputs may be gated by the switch to the single common output. The switch contains two stages of amplification. The input amplifier consists of a transistor for amplifying the input signal applied to its base, and a current control transistor for starving or supplying current to the input transistor. When the input transistor is turned off by current starvation, the off condition of each input amplifier is sensed by a bias circuit. The bias circuit feeds back a voltage level to the collector of the input transistor insuring that the collector - base junction of the input transistor is reverse biased. The second amplifier is an isolation amplifier configured as an emitter follower OR circuit. When the off condition of the input transistor is sensed, the isolation amplifier is reverse biased across its emitter-base junction. Thus, an amplifying stage controlled by current starvation and an amplifying stage performing a logical OR function have been combined with a bias arrangement enabling both amplifiers to be driven on with wide band characteristics, or to be reverse biased off to achieve high isolation.</p> |
