US Patent 7286017 Controllable RF broadband and amplifier with a constant input impedance

A variable-gain RF amplifier arrangement whose input impedance is essentially independent of the selected gain is proposed, which has a large number of selectable elementary amplifiers, with an input signal being scaled and the input impedance being set to be the same by means of switchable current limiting elements upstream of the elementary amplifiers, which are associated with the elementary amplifiers. The circuit also has a low noise level, which is largely independent of the selected gain, and good linearity. A broadcast radio receiver as well as a receiver for receiving data signals using an amplifier according to the invention are also proposed.