RF-Input stage

摘要

RF-input stage for TV receivers comprising a field effect transistor in grounded source circuit configuration and a frequency-dependent coupling network arranged between the gate electrode of the field effect transistor and an aerial input for selecting TV signals and transforming the signal impedance. The frequency-dependent coupling network is terminated with a resistor which is arranged between the gate electrode of the field effect transistor and ground and whose value has been chosen so that on the one hand this resistor terminates in conjunction with the input impedance of the field effect transistor the frequency-dependent coupling network with an acceptable reflection factor and on the other hand forms in conjunction with the output impedance of the frequency-dependent coupling network an impedance at which the noise contribution of the field effect transistor is at least substantially at its lowest. This results in a small impedance transformation of the frequency-dependent coupling network and makes it possible to construct this coupling network in a wideband mode.