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 obtained with the crucial parts of a single chip solution. The circuit was produced in an 80 V bipolar process. Distortion artefacts were reduced 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 transistors used in microphone output stages are compared with measurements and simulations.
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