| 摘要 |
A differential to single-ended converter circuit comprises a first operational amplifier OA1 which acts as a summer and a second op-amp OA2 which acts as an inverter. A first converter input 84 is coupled to an inverting input of the first operational amplifier, and a second converter input 86 is coupled to an inverting input of the second operational amplifier, while a converter output is taken from the output of the first operational amplifier. The output of the second operational amplifier is coupled to the inverting input (summing point) of the first operational amplifier. In prior art, the non-inverting input of the second operational amplifier would be connected to ground. In the present invention it is coupled to the inverting input of the first operational amplifier. The has the result that the gain for noise signals Vn1 appearing at the non-inverting input of the first op-amp may be set to unity and that the current through the feedback impedance 90 of the first op-amp is independent of noise on the non-inverting input of the first operational amplifier. The circuit arrangement allows relaxation of performance requirements of the first op-amp, which may drive a loudspeaker 34. |
