Abstract: A combination of a microphone and a sigma-delta A/D converter include at least one feedback loop, such as a DC feedback loop. The DC feedback loop provides the bias current for a junction FET of the microphone. In this way, the signal current from the FET can be injected directly into the input integrator of the sigma-delta A/D converter without the need of signal resistors in series with the FET.

Abstract: A combination of an electret microphone (1) and a sigma-delta A/D converter (9, 5, 7, 8). The sigma-delta A/D converter has a DC feedback loop (8) which provides the bias current (IDC) for the junction FET (2) of the electret microphone. In this way the signal current from the FET (2) can be injected directly into the input integrator (9) of the sigma-delta A/D converter without the need of signal resistors in series with the FET (2).

Abstract: A quadrature device 1 for a communication device, receiver, transmitter, transceiver, telephone, mixer, modulator or demodulator comprises I and Q signal paths and corresponding signal paths components 2I, 2Q; 4I, 4Q; 9I, 9Q showing a mismatch. The device 1 comprises switching means 3, 3′, 6, 3″, 3′″ for in particular data dependently exchanging the I and Q signals in said I and Q paths in order to improve adverse effects, such as reduction of leakage of quantisation noise from the image band to the signal band in a quadrature modulator. Even mismatch effects between digital to analog converters (DAC's) in a feedback path of a sigma delta (&Sgr;&Dgr;) modulator are compensated.