Abstract: The output impedance of an amplifier is substantially matched to an input impedance of a receiver using a buffer circuit. The buffer circuit includes a primary transistor and a secondary transistor. A first back gate terminal of the primary transistor is coupled to a second back gate terminal of the secondary transistor and the primary transistor is configured to have an output for the buffer circuit. An input signal is received from the amplifier at a gate terminal of the secondary transistor. The first back gate terminal of the primary transistor is responsively driven independently from the output of the buffer circuit to effectively adjust a transconductance of the primary transistor and substantially match an output impedance of the amplifier with an input impedance of the receiver.

Abstract: The output impedance of an amplifier is substantially matched to an input impedance of a receiver using a buffer circuit. The buffer circuit includes a primary transistor and a secondary transistor. A first back gate terminal of the primary transistor is coupled to a second back gate terminal of the secondary transistor and the primary transistor is configured to have an output for the buffer circuit. An input signal is received from the amplifier at a gate terminal of the secondary transistor. The first back gate terminal of the primary transistor is responsively driven independently from the output of the buffer circuit to effectively adjust a transconductance of the primary transistor and substantially match an output impedance of the amplifier with an input impedance of the receiver.

Abstract: The output impedance of an amplifier is substantially matched to an input impedance of a receiver using a buffer circuit. The buffer circuit includes a primary transistor and a secondary transistor. A first back gate terminal of the primary transistor is coupled to a second back gate terminal of the secondary transistor and the primary transistor is configured to have an output for the buffer circuit. An input signal is received from the amplifier at a gate terminal of the secondary transistor. The first back gate terminal of the primary transistor is responsively driven independently from the output of the buffer circuit to effectively adjust a transconductance of the primary transistor and substantially match an output impedance of the amplifier with an input impedance of the receiver.

Abstract: A buffer circuit includes a buffering portion, an active resistor, and a control portion. The buffering portion is configured to receive a signal from a microphone. The active resistor is coupled to the buffering portion and the control portion is coupled to the active resistor. The control portion is configured to selectively activate or deactivate the active resistor. When the active resistor is activated, the active resistor and a capacitance of the microphone form a high pass filter. The high pass filter is effective to filter noise from the signal received from the microphone by the buffering portion.

Abstract: The output impedance of an amplifier is substantially matched to an input impedance of a receiver using a buffer circuit. The buffer circuit includes a primary transistor and a secondary transistor. A first back gate terminal of the primary transistor is coupled to a second back gate terminal of the secondary transistor and the primary transistor is configured to have an output for the buffer circuit. An input signal is received from the amplifier at a gate terminal of the secondary transistor. The first back gate terminal of the primary transistor is responsively driven independently from the output of the buffer circuit to effectively adjust a transconductance of the primary transistor and substantially match an output impedance of the amplifier with an input impedance of the receiver.

Abstract: A microphone buffer circuit being adaptable for connection to a power source is disclosed. The microphone buffer circuit includes an input transistor operably connected between an input and an output for buffering an input signal. The microphone buffer circuit includes a means for reducing power supply noise capable of being coupled to the input transistor wherein the means being operably connected to the input transistor and the power source.

Abstract: A hybrid circuit (300) for use in a miniature microphone assembly (100) reduces power supply noise on the audio signal input (214) of an impedance buffer amplifier (200) using one or both of shielding conductors 422, 424 to reduce parasitic capacitance between signal (418) and power supply (420) conductors. A ground plane (424), an interposing conductor (422) and combinations thereof are selectively placed and coupled to either ground (232) or a low impedance signal node (216) to reduce or eliminate the undesirable parasitic capacitance.

Abstract: A system and method for assisting listening wherein an integrated circuit selects one or more audio sources from among a plurality audio sources to be presented to a signal processing circuit. Selection of the audio source can be automatically executed in response to detection of an external magnetic field, such as from a telephone handset, or manually controlled by a user input.

Abstract: A first circuit stage comprises at least one NMOS transistor and is coupled to a microphone transducer. A coupling circuit is coupled to the first circuit stage. A second circuit stage is adapted to receive signals from the first circuit stage via the coupling circuit and buffer the signals. The first circuit stage, the second circuit stage, and the coupling circuit reside completely within a microphone housing. A first contact member extends externally from the microphone housing and is electrically coupled to an output of the second circuit stage. The first contact member is adapted to selectively receive power from an external power supply to power the microphone circuit.

Abstract: An input biasing circuit for a microphone is disclosed. The circuit includes an input and an output. An input transistor is connected between the input and the output and to a biasing circuit. The biasing circuit DC biases the gate terminal of the input transistor. A resistor operably connected to, and cooperating with the input transistor, provides a buffered version of a received microphone transducer signal to the output.

Abstract: A system and method for assisting listening wherein an integrated circuit selects one or more audio sources from among a plurality audio sources to be presented to a signal processing circuit. Selection of the audio source can be automatically executed in response to detection of an external magnetic field, such as from a telephone handset, or manually controlled by a user input.

Abstract: A method and apparatus for substantially reducing and virtually eliminating direct current flow through the input transistor(s) of an input buffer circuit for an electret microphone is disclosed. An input transistor is provided and operably connected to an input and an output of the input buffer circuit. The input transistor has a first operating state wherein current flow occurs in a first direction and a second operating state wherein the a current flow occurs in a second direction—opposite that of the first direction. The input transistor is biased to alternately control operation between the first operating state and the second operating state. The alternating, opposing flows of current of the respective operating states cooperate to substantially reduce and virtually eliminate the flow of direct current through the input transistor(s) of the buffer circuit.

Abstract: A magnetic field sensor includes a transistor device having a base region, an emitter region, and a collector region. A barrier region disposed between the emitter region and the collector region to hamper charge carriers injected into the base region from the emitter region from reaching at least a portion of the collector region. The magnetic field sensor further includes a first voltage source to bias the collector region with respect to the base region to form a space-charge layer associated with the collector region.

Abstract: A hybrid circuit (300) for use in a miniature microphone assembly (100) reduces power supply noise on the audio signal input (214) of an impedance buffer amplifier (200) using one or both of shielding conductors 422, 424 to reduce parasitic capacitance between signal (418) and power supply (420) conductors. A ground plane (424), an interposing conductor (422) and combinations thereof are selectively placed and coupled to either ground (232) or a low impedance signal node (216) to reduce or eliminate the undesirable parasitic capacitance.

Abstract: A magnetic field sensor includes a transistor device having a base region, an emitter region, and a collector region. A barrier region disposed between the emitter region and the collector region to hamper charge carriers injected into the base region from the emitter region from reaching at least a portion of the collector region. The magnetic field sensor further includes a first voltage source to bias the collector region with respect to the base region to form a space-charge layer associated with the collector region.

Abstract: A method and system for adjusting the frequency response characteristics of a transducer assembly (312) is disclosed. The transducer assembly (312) includes a modifiable buffer circuit (100) being generally enclosed within a housing (314). Electrical signal connections for modifying the operating state of the modifiable buffer circuit (100) are accessible outside the housing (314). The modifiable buffer circuit (100) further includes a plurality of signal inputs (234) and outputs (230), the plurality of signal inputs (234) are accessible from outside the housing. A predetermined relationship exists between the plurality of signal inputs (234) and the plurality of outputs (230). A resistor network (224) is operably connected to the plurality of outputs (230) wherein a portion of the resistor network (224) is operably disconnected from a filter network (218) in response to the plurality of signal inputs (234).

Abstract: A method and system for adjusting the frequency response characteristics of a modifiable buffer circuit (100) is disclosed. The modifiable buffer circuit (100) being generally enclosed within a housing (316). Electrical signal connections for modifying the operating state of the modifiable buffer circuit (100) are accessible outside the housing (316). The modifiable buffer circuit (100) further includes a plurality of signal inputs (234) and outputs (230), the plurality of signal inputs (234) are accessible from outside the housing. A predetermined relationship exists between the plurality of signal inputs (234) and the plurality of outputs (230). A resistor network (224) is operably connected to the plurality of outputs (230) wherein a portion of the resistor network (224) is operably disconnected from a filter network (218) in response to the plurality of signal inputs (234).

Abstract: A system and method for assisting listening wherein an integrated circuit selects one or more audio sources from among a plurality audio sources to be presented to a signal processing circuit. Selection of the audio source can be automatically executed in response to detection of an external magnetic field, such as from a telephone handset, or manually controlled by a user input.

Abstract: A microphone buffer circuit being adaptable for connection to a power source is disclosed. The microphone buffer circuit includes an input transistor operably connected between an input and an output for buffering an input signal. The microphone buffer circuit includes a means for reducing power supply noise capable of being coupled to the input transistor wherein the means being operably connected to the input transistor and the power source.

Abstract: A method and apparatus for substantially reducing and virtually eliminating direct current flow through the input transistor(s) of an input buffer circuit for an electret microphone is disclosed. An input transistor is provided and operably connected to an input and an output of the input buffer circuit. The input transistor has a first operating state wherein current flow occurs in a first direction and a second operating state wherein the a current flow occurs in a second direction—opposite that of the first direction. The input transistor is biased to alternately control operation between the first operating state and the second operating state. The alternating, opposing flows of current of the respective operating states cooperate to substantially reduce and virtually eliminate the flow of direct current through the input transistor(s) of the buffer circuit.