Amplifier circuit (1) for
broadband and low-
noise amplification of a
capacitive current source, comprising a
signal input (3) which can be connected to the
capacitive current source in a node K1, an input stage (A1), wherein the input stage (A1) is connected to the node K1 at an input (7) of the input stage (A1) and has a node K2 at the output (9) of the input stage (A1), wherein the input stage (A1) is arranged to amplify an input
voltage at least 3 times, wherein the input stage (A1) is arranged to provide a high-impedance input
resistor at the input of the input stage (A1), wherein the input stage (A1) is arranged to provide a stable and load-independent
voltage at the output of the input stage (A1), an
amplifier cascade, wherein the
amplifier cascade (11) has at least a first and a second
amplifier (A2, A3), each with an input (13, 17) and an output (15, 19), wherein the output (15) of the first amplifier (A2) is connected in a node K3 to the input (17) of the second amplifier (A3), wherein the input (13) of the first amplifier (A2) is connected to the node K2, wherein the output (19) of the second amplifier (A3) is connected to a node K4, wherein the amplifier
cascade (11) is arranged to generate a high
signal amplification with low phase shift over a wide frequency range, a feedback network (F1), wherein the feedback network (F1) is connected to the input (7) of the input stage (A1) in node K1 and the output (19) of the second amplifier (A3) in node K4, wherein the feedback network (F1) is arranged to provide a high-ohmic feedback
resistor with a
parasitic capacitance of less than 0.5 pF, wherein the feedback network (F1) is arranged to provide a
negative feedback to a structure comprising the input stage (A1) and the amplifier cascade (11), and a
signal output (21) connected to a node K5, wherein the node K5 is connected to the node K4 or corresponds to the node K4, wherein the input stage (A1) comprises a junction
field effect transistor (Q1) and a bipolar
transistor (Q2), wherein a drain terminal of the junction
field effect transistor (Q1) is connected to a base terminal of the bipolar transistor, wherein the junction
field effect transistor (Q1) is connected as a source circuit, wherein the bipolar transistor (Q2) is connected as an emitter follower, wherein the first and second amplifiers (A2, A3) of the amplifier cascade (11) are operational amplifiers (Q3, Q4), wherein the first
operational amplifier (Q3) has a
voltage gain of more than 10 4 has, wherein the second
operational amplifier (Q4) has a voltage
gain of maximum 10 3 has, wherein the feedback network (F1) has a high-
ohm feedback
resistor with a parallel
capacitance, wherein the feedback network (F1) comprises a series-connected low-pass filter.