| 摘要 |
In signal sources having a high impedance, typically a capacitive "signal source" such as capacitor-microphone capsules, it is common practice to use amplifier circuits that include means for coupling signals and determining operating points in addition to the actual amplifier having a high-resistance, non-inverting input. For setting the operating points of the signal source and the amplifier, separate bias-voltage sources are provided; these are coupled to the signal source and the non-inverting input, respectively, of the amplifier via a coupling impedance. At least one coupling capacitance is disposed in the signal path between the signal source and the non-inverting input of the amplifier. To attain a considerable noise gain without the disadvantage of very high idle times in this type of amplifier circuit, it is proposed that the coupling impedances be formed from a nonlinear resistance (D1, D2 or D3, D4) and an ohmic resistance (R3 or R4) connected thereto in series. Moreover, the output signal (S2) of the amplifier (ICI) or a signal derived therefrom is fed back to the coupling impedances (D1, D2, R3 or D3, D4, R4) via a second or third coupling capacitance (C3 or C4). |
