Patent ID: 7253682

Claim:
An antenna amplifier for mobile FM radio reception, comprising: a signal amplifier; an adjusting element including: at least one PIN diode for adapting an impedance of an antenna to an impedance of a signal amplifier, a first adaptation system for adapting the impedance of the antenna to an impedance of the at least one PIN diode, and a second adaptation system for adapting the impedance of the at least one PIN diode to the impedance of the signal amplifier; a control amplifier for regulating the adjusting element; four resistors, wherein: the operational amplifier of the control amplifier and the four resistors form a subtracter having a first input voltage at a second input and a second input voltage at a first input of the control amplifier; and two diodes representing voltage sources connected in series with inputs of the operational amplifier, each of the two diodes being traversed by an approximately identical quiescent current that is determined by respective voltages and resistors, the two diodes being thermally coupled in mechanical fashion in such a way that the two diodes have approximately identical temperature coefficients, wherein: a HF voltage coupled out at an output of the signal amplifier produces at one of the two diodes a rectified voltage that is amplified by a factor; wherein the control amplifier includes: a rectifier for a rectified voltage, and an operational amplifier that amplifies the rectified voltage.