Circuit assembly for correction of an input signal, use of the circuit assembly for detection of a physiological signal in a magnetic resonance (MR) system

A circuit assembly for correction of an input signal, wherein the input signal at an input interface (Li_in) of the circuit assembly comprises a useful signal and a disturbance signal, wherein the circuit assembly comprises:

• a voltage-controlled circuit(S) having at least one voltage-controlled circuit element (T1, T2), having a first terminal (K) and a low-resistance second terminal (E), said at least one voltage-controlled circuit element comprising at least one transistor, wherein the first terminal (K) is a collector terminal of the at least one transistor and the second terminal (E) is an emitter terminal of the at least one transistor, the at least one voltage-controlled circuit element (T1, T2) further comprising a control input (B) that is the base terminal of the at least one transistor, the control input (B) being electrically connected to the input interface (Li_in) via a control resistor (R1),
• a resistor (R2) connected upstream of the voltage-controlled circuit(S) in series with the voltage-controlled circuit(S), the resistor (R2) electrically connecting the input interface (Li_in) to the first terminal (K) of the at least one transistor,
• an operational amplifier (U1) having a first amplifier input (VE+), a second amplifier input (VE−) and an amplifier output (VA), and
• a low-pass filter (R3-C1) connected between the first terminal (K) of the at least one voltage-controlled circuit element (T1, T2) and the first amplifier input (VE+) of the operational amplifier (U1),
• wherein the output voltage from the operational amplifier (U1) is fed back to the low-resistance terminal (E) of the circuit element (T1, T2) in that the low-resistance terminal (E) of the at least one voltage-controlled circuit element (T1, T2) is electrically connected to the amplifier output (VA) of the operational amplifier (U1) and to the second amplifier input (VE−) of the operational amplifier (U1).