Microphone preamplifier
AssigneeTaylor Hohendahl Engineering LLP
InventorAndres Hohendahl
Life of this patent
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Abstract
A microphone preamplifier. An electrical signal from a microphone is received via a shielded cable by an input stage cascaded with an output stage. The input stage contains an impedance converter and a phase inverter and receives feedback that reduces input capacitance, actively shields the coaxial cable, and stabilizes the input stage. The output stage contains a buffer and output driver and provides amplified versions of the input stage output. The preamplifier contains means for transformerless phantom powering the microphone and the microphone preamplifier, for sharing current between the input and the output stages, and for limiting the frequency at the output of the microphone.
Claims24
A microphone preamplifier, comprising:
- a cascade of an input stage and an output stage wherein the input stage has an input capacitance, receives an input signal from a microphone through a coaxial cable, and generates as input-stage output an in-phase output signal and an inverted-phase output signal and the output stage generates an amplified in-phase output signal and an amplified inverted-phase output signal;
- means for transformerless phantom powering of the microphone and the microphone preamplifier;
- means for sharing current between the input and output stages;
- means for actively feeding back input-stage output wherein the input capacitance is lowered;
- means for actively feeding back input-stage output wherein the coaxial cable is actively shielded;
- and
- means for negatively feeding back input-stage output wherein the input stage is stabilized.
A microphone preamplifier, comprising:
- phase inverter comprising a cascode and a first transistor, wherein the phase inverter receives an electrical signal from a means of producing the electrical signal from sound pressure, produces inverter output comprising an in-phase output signal and an inverted-phase output signal of the electrical signal, and receives a first feedback and a second feedback of the inverter output;
- coaxial cable comprising a wire communicating the electrical signal to the phase inverter and a shield receiving a third feedback of the inverter output;
- a driver stage comprising a second and a third transistor wherein the second transistor receives the in-phase output signal and produces an amplified in-phase output signal and the third transistor receives the inverted-phase output signal and produces an amplified inverted-phase output signal;
- an input-stage power-supply conditioner receiving a residual current from the driver stage and supplying a voltage and current to the phase inverter;
- first upper frequency limiter, wherein the first upper frequency limiter receives the amplified in-phase output signal and generates a preamplifier in-phase output signal;
- a second upper frequency limiter, wherein the second upper frequency limiter receives the amplified inverted-phase output signal and generates a preamplifier inverted-phase output signal;
- and
- a polarization power supply communicating with the first and second upper frequency limiters and supplying voltage to the means for producing an electrical signal.
Dependencies are inferred from the claim text.