| 摘要 |
<p>In transconductance amplifier arrangements used in CATV systems, it is often desirable to set the value of the output impedance to a value equal to the system impedance that is often 75 Φ. Prior art transconductance amplifiers often comprise an amplifier (6) with a current output using a feedback network (8) to set the gain value. An input of the feedback network (8) is coupled to the current output of the amplifier (6) and an output of the feedback network (8) is coupled to the input of the amplifier (6). In these prior art transconductance amplifier arrangements the output impedance decreases with increasing gain of the amplifier (6) used in the amplifier arrangement. This output impedance is normally very low (a few Φ or lower). By adding a further output current (i/N) to the output of the feedback network, it is obtained that the current through the feedback network (8) becomes dependent on the output current (i) of the amplifier. This dependence results in an increased output impedance.</p> |
