Loudspeakers and Microphones
A phantom power supply increases the load on the output circuit of a condenser microphone and produces harmonic distortion. This effect can be cancelled by substituting two controlled current sources for the phantom power supply that reduce the load on the microphone output.
This article presents measurements from the crucial part of a single chip solution, produced in an 80 V bipolar process. The circuit reduces distortion artefacts by up to 4 dB.
A theoretical derivation for predicting the distortion of a phantom power circuit is given. Calculations based on the nonlinearity of the microphone output circuit are compared with measurements and simulations.