Hearing aid

In a hearing aid including first transducer means for producing a signal representative of sound, amplifier means for amplifying the signal produced by said first transducer means and second transducer means for producing sounds representative of the sound sensed by said first transducer means at an amplified level in response to said amplified signal produced by said amplifier means, the improvement comprising said first transducer means including microphone means for producing sound signals in response to the sound sensed thereby and microphone input circuit means coupled to said microphone means for applying signals representative of the sound sensed by said microphone means to said amplifier means, said microphone input circuit means including at least one pair of MOS field-effect transistors having a commonly coupled drain terminal defining an output to be coupled to said amplifier means, and a gate electrode of one of said transistors being coupled to said microphone means to receive said sound signals therefrom in response to the sound sensed thereby the gate electrode of said MOS transistor not coupled to said microphone means being coupled to the commonly coupled drain output of the microphone input circuit means to thereby stabilize the operation thereof, a further microphone means for producing a sound signal representative of the sound sensed thereby, and additional input circuit means for receiving said sound signals produced by said further microphone means, said additional input circuit means including a second pair of MOS transistors, said first and second pairs of transistors having their respective gate electrodes coupled together to define first and second inputs to be respectively coupled to said first mentioned microphone means and further microphone means to receive the sound signal produced thereby, the drain terminal of each of said transistors in said first and second pairs of transistors being coupled together to define an output to be coupled to said amplifier means for producing a signal representative of the sound sensed by said first mentioned microphone means and said additional microphone means.

A hearing aid including first transistor means for producing a signal representative of sound, amplifier means for producing an amplified signal in response to the signal produced by said first transducer means, and second transducer means for producing sounds representative of the sound sensed by said first transducer means at an amplified level in response to said amplified signal produced by said amplifier means, the improvement comprising said second transducer means including earphone means for producing sound in response to a driving signal applied thereto, and amplifier-drive circuit means coupled to said amplifier means for receiving said amplified signal produced thereby and applying an amplified drive signal to said earphone means, said amplifier-drive circuit means including a first P-channel field-effect MOS drive transistor and a second N-channel MOS field-effect drive transistor having commonly coupled drain electrodes for defining a drive output for applying a drive signal to said earphone means, and including at least one pair of coupled first MOS transistor means defining an input for said amplifier-drive circuit means for receiving the amplified signal produced by said amplifier means, and a second P-channel transistor coupled in series with one of said first MOS transistor means, the junction between said second P-channel MOS transistor means and said first-transistor means of said pair being coupled to said P-channel drive transistor means, and a second N-channel transistor means coupled to the other first transistor means of said pair of transistor means defining said input, the junction therebetween being coupled to the gate electrode of said N-channel drive transistor.

In a hearing aid including first transducer means for producing a signal representative of sound, amplifier means for amplifying the signal produced by said first transducer means and second transducer means for producing sounds representative of the sound sensed by said first transducer means at an amplified level in response to said amplified signal produced by said amplifier means, the improvement comprising said first transducer means including microphone means for producing sound signals in response to the sound sensed thereby and microphone input circuit means coupled to said microphone means for applying signals representative of the sound sensed by said microphone means to said amplified means, said microphone input circuit means including at least one pair of MOS field-effect transistors having a commonly coupled drain terminal defining an output to be coupled to said amplifier means, and a gate electrode of one of said transistors being coupled to said microphone means to receive said sound signals therefrom in response to the sound sensed thereby, the gate electrode of said MOS transistor not coupled to said microphone means being coupled to the commonly coupled drain output of the microphone input circuit means to thereby stabilize the operation thereof, a further microphone means for producing a sound singal representative of the sound sensed thereby, said input circuit means including a second pair of MOS transistors having commonly coupled gate electrodes adapted to be coupled to said further microphone means to receive the sound signal produced thereby, the respective gate electrodes of said first pair of MOS field-effect transistors being coupled together and adapted to receive the sound signal produced by said first-mentioned microphone means, said first and second transistors of said second pair being respectively coupled in series to said first and second MOS transistors of said first pair so that the drain outputs of said first pair of MOS field-effect transistors define an output of the microphone input circuit means for producing a signal representatve of the sound sensed by said first-mentioned microphone means and said further microphone means.