Patent ID: 7005895

Claim:
Driver circuit for driving a useful signal having: (a) a signal input for applying a useful signal; (b) at least one amplifier circuit with low output impedance for the signal amplification of the useful signal, wherein the amplifier circuit is an operational amplifier having an inverting signal input, a non-inverting signal input and a signal output, wherein one of the signal inputs of the operational amplifier is connected with the signal input for applying the useful signal; (c) a protection impedance respectively connected downstream of the amplifier circuit and serving to protect the amplifier circuit, wherein the protection impedance is connected between the signal output of the operational amplifier and a signal line connection for connecting a signal line, wherein the signal line is a telephone line for connecting a telephone to the driver circuit; wherein (d) provision is respectively made of a feedback circuit for a frequency-dependent signal feedback of the useful signal amplified by the amplifier circuit; wherein (e) the signal feedback circuit respectively has a capacitor, which is connected between the signal output of the operational amplifier and the other one of the signal inputs of the operational amplifier not connected to the useful signal, and a resistor, which is connected between the signal line connection and the signal input of the operational amplifier.