Abstract: A circuit according to an example includes an immitance converter amplifier based on a plurality of transistors of a first conductivity type and a supply transistor coupled between an output of the immitance converter amplifier and a supply for a supply potential, the supply transistor being a transistor of a second conductivity type complementary to the first type.

Abstract: A circuit according to an example includes an immitance converter amplifier based on a plurality of transistors of a first conductivity type and a supply transistor coupled between an output of the immitance converter amplifier and a supply for a supply potential, the supply transistor being a transistor of a second conductivity type complementary to the first type.

Abstract: A low-noise amplifier circuit is specified which has a switchable gain ratio. For this purpose, a parallel circuit comprising a first and a second current path (3, 4) is provided between a radio-frequency signal input and output (1, 2), with the first current path (3) having a transistor which is connected in a common-base circuit for signal amplification, and the second current path (4) having a transistor which is connected in a common-emitter circuit (7) for signal amplification, and has input impedance matching (25, 27). Owing to the good noise characteristics and the good linearity characteristics, the described low-noise amplifier circuit is suitable for use in radio-frequency receivers in which adaptive pre-amplification is required even before a frequency converter, that is to say at the radio-frequency level, because the input signal has a wide dynamic range, such as that in the case of UMTS.