A detection circuit for detecting a clock signal includes a multiplexer, a digital-to-analog converter, a comparator, and a counter. The multiplexer outputs either a first signal or a second signal as a selection signal. The digital-to-analog converter outputs a reference voltage according to the selection signal. The comparator compares the clock signal to the reference voltage to generate a comparison signal. The counter counts a reference clock signal to generate an overflow signal, and resets the overflow signal according to the comparison signal. The overflow signal indicates the amplitude of the clock signal.

A detection circuit for detecting a clock signal includes a multiplexer, a digital-to-analog converter, a comparator, and a counter. The multiplexer outputs either a first signal or a second signal as a selection signal. The digital-to-analog converter outputs a reference voltage according to the selection signal. The comparator compares the clock signal to the reference voltage to generate a comparison signal. The counter counts a reference clock signal to generate an overflow signal, and resets the overflow signal according to the comparison signal. The overflow signal indicates the amplitude of the clock signal.

An integration unit IU for tuning an OEM sound system augmented with aftermarket components, such as an amplifier or a subwoofer. The integration unit is contained in a small housing that can be installed inconspicuously in most vehicles without removing the original head unit. The unit may comprise a DSP-based active line output converter that is configured to automatically detect the frequency response and phase of the OEM head unit. The unit performs various algorithms to detect and analyze crossovers, EQ, time delay, and allpass filters and then matches left and right audio channels. The IU may allow for low bass correction detecting and defeating the factory high pass filter. Still further, the IU can correct the various filters to ensure a clean, uncolored audio signal for the augmented components.

An audio amplifier with duty ratio control is provided. The audio amplifier comprises a pulse width modulation modulator, a power stage, and a voltage converter. The pulse width modulation modulator is configured to receive an input signal for generating a pulse width modulation signal. The power stage is configured to output an output signal according to a supply voltage and the pulse width modulation signal. The voltage converter is configured to adjust voltage level of the supply voltage according to the pulse width modulation signal. The audio amplifier is configured to adjust the voltage level of the supply voltage when duty ratio of the pulse width modulation signal is greater than a duty ratio threshold.

Disclosed are systems and methods for a variable-gain differentiator in series with at least two non-inverting amplifiers. The variable-gain differentiator is connected to a voltage-controlled source at its non-inverting input and to its output at its inverting input. The output is connected to the non-inverting input of the first non-inverting amplifier. The output of the first non-inverting amplifier is connected to the input of the second non-inverting amplifier. The output of the second non-inverting amplifier is connected to a series of three integrators. Each integrator is connected to its output by a feedback path. Varying the gain of the voltage-controlled amplifier varies the gain of the differentiator at the output of the third integrator, thereby varying the output of the system.

Disclosed are systems and methods for a variable-gain differentiator in series with at least two non-inverting amplifiers. The variable-gain differentiator is connected to a voltage-controlled source at its non-inverting input and to its output at its inverting input. The output is connected to the non-inverting input of the first non-inverting amplifier. The output of the first non-inverting amplifier is connected to the input of the second non-inverting amplifier. The output of the second non-inverting amplifier is connected to a series of three integrators. Each integrator is connected to its output by a feedback path. Varying the gain of the voltage-controlled amplifier varies the gain of the differentiator at the output of the third integrator, thereby varying the output of the system.

An audio preamplifier (1) for a microphone, including: a chassis (2) with at least one audio input (17) and at least one audio output, a control panel (3) including a gain selector (10) being arranged on one of the sides of the chassis (2), the chassis (2) further including a receiving compartment inside which a first connector is arranged; and a cartridge (6) comprising a preamplification circuit and a gain control circuit, the cartridge (6) further having a second connector complementary to the first connector, the cartridge (6) being configured for being inserted in a removable manner into the receiving compartment of the chassis (2) so as to connect the first and second connectors. An audio preamplification kit includes an audio preamplifier (1) and a plurality of additional cartridges.

Apparatus and methods for biasing of low noise amplifiers (LNAs) are provided herein. In certain embodiments, an LNA includes at least one transistor that amplifies a radio frequency (RF) input signal, and a bias circuit including a current bias circuit that generates a bias current based on a reference current and a voltage bias circuit that generates at least one input bias voltage for the at least one transistor based on the bias current. The current bias circuit includes a first bias transistor that receives the reference current, a second bias transistor that generates the bias current, and an amplifier that controls a first bias voltage of the first bias transistor to match a second bias voltage of the second bias transistor.

Apparatus and methods for biasing of low noise amplifiers (LNAs) are provided herein. In certain embodiments, an LNA includes at least one transistor that amplifies a radio frequency (RF) input signal, and a bias circuit including a current bias circuit that generates a bias current based on a reference current and a voltage bias circuit that generates at least one input bias voltage for the at least one transistor based on the bias current. The current bias circuit includes a first bias transistor that receives the reference current, a second bias transistor that generates the bias current, and an amplifier that controls a first bias voltage of the first bias transistor to match a second bias voltage of the second bias transistor.

Methods and systems for performing automatic speed-based audio control. One method includes receiving, with an electronic control unit included in a vehicle, a speed of the vehicle and receiving, with the electronic control unit, an audio signal. The method also includes accessing, with the electronic control unit, a plurality of equalization curves based on the speed of the vehicle, each of the plurality of equalization curves associated with the speed of the vehicle and each of the plurality of equalization curves defining a gain adjustment for one of a plurality of frequencies, and, for each curve of the plurality of equalization curves, applying the gain adjustment defined by the curve to one of the plurality of frequencies of the audio signal.