Multiple stage hearing aid transistor amplifier having signal voltage controlled frequency dependent network

Claim 2

A multi-stage transistor amplifier for a hearing aid comprising in combination: a. means for deriving from a point in said amplifier an audio frequency voltage whose amplitude is proportional to that of the audio frequency signal at a point along the forward amplification path of the amplifier; b. means for converting said audio frequency voltage into a d.c. control voltage; c. a circuit network including a frequency dependent negative feedback circuit connected in the amplifier for influencing the frequency response thereof in the voice frequency range, said circuit including a capacitance as its only reactive element and having a frequency characteristic which is free of any resonance in the voice frequency range; and d. means for applying said control voltage to said frequency dependent circuit, whereby the frequency characteristics of said frequency dependent circuit are varied in response to changes in the amplitude of said audio frequency voltage.

Claim 3

A multi-stage transistor amplifier as defined in claim 1, wherein said negative feedback circuit is connected between the collector and the base of a transistor in an amplification stage.

Claim 4

A multi-stage transistor amplifier as defined in claim 2, wherein said frequency dependent circuit in said negative feedback circuit includes means whose electrical resistance is changed in response to changes in the amplitude of the control voltage.

Claim 5

A multi-stage transistor amplifier as defined in claim 3, wherein said means whose electrical resistance can be changed comprises the emitter-collector path of a second transistor, controlled by the d.c. control voltage.

Claim 6

A multi-stage transistor amplifier as defined in claim 2, wherein said frequency dependent circuit in said negative feedback circuit includes a capacitor and a variable resistor connected in series.

Claim 7

A multi-stage transistor amplifier for a hearing aid comprising in combination: a. means for deriving from a point in said amplifier an audio frequency voltage whose amplitude is proportional to that of the audio frequency signal at a point along the forward amplification path of the amplifier; b. means for converting said audio frequency voltage into a d.c. control voltage; c. a circuit network including a frequency-dependent voltage divider operatively connected between the output of one stage of said amplifier and the input of the next succeeding stage of said amplifier for influencing the frequency response thereof in the voice frequency range, said divider including a series resistor connected between the output of said one stage and the input of said next succeeding stage, and a shunt resistor having one end connected to a point between said series resistor and said next succeeding stage input, one of said resistors being an electronically adjustable element whose resistance is changed in response to a voltage applied thereto, said circuit including a capacitance as its only reactive element and having a frequency characteristic which is free of any resonance in the voice frequency range; and d. means for applying said control voltage to said adjustable element of said frequency-dependent circuit, whereby the frequency characteristics of said frequency-dependent circuit are varied in response to changes in the amplitude of said audio frequency voltage.

Claim 8

A multi-stage transistor amplifier for a hearing aid comprising in combination: a. means for deriving from a point in said amplifier an audio frequency voltage whose amplitude is proportional to that of the audio frequency signal at a point along the forward amplification path of the amplifier; b. means for converting said audio frequency voltage into a d.c. control voltage; c. a circuit network including a frequency-dependent voltage divider operatively connected between the output of one stage of said amplifier and the input of the next succeeding stage of said amplifier for influencing the frequency response thereof in the voice frequency range, said divider including a series resistor connected between the output of said one stage and the input of said next succeeding stage, and a shunt resistor having one end connected to a point between said series resistor and said next succeeding stage input, one of said resistors being an electronically adjustable element whose resistance is changed in response to a voltage applied thereto, said circuit including a capacitance as its only reactive element and having a frequency characteristic which is free of any resonance in the voice frequency range; and d. means for applying said control voltage to said adjustable element of said frequency-dependent circuit, whereby the frequency characteristics of said frequency-dependent circuit are varied in response to changes in the amplitude of said audio frequency voltage.

Claim 9

A multi-stage transistor amplifier as defined in claim 6 wherein said adjustable element constitutes said shunt resistor and said capacitance comprises a capacitor connected in series with said adjustable element.

Claim 10

A multi-stage transistor amplifier as defined in claim 7 wherein said adjustable element comprises the emitter-collector path of a transistor whose base is connected to receive said d.c. control voltage to cause the resistance of said adjustable element to be controlled by said control voltage.

Claim 11

A multi-stage transistor amplifier as defined in claim 6 wherein said adjustable element constitutes said series resistor and said capacitance comprises a capacitor connected in parallel with said series resistor.

Claim 12

A multi-stage transistor amplifier as defined in claim 9 wherein said adjustable element comprises the emitter-collector path of a transistor whose base is connected to receive said d.c. voltage to cause the resistance of said adjustable element to be controlled by said control voltage.

Claim 13

A multi-stage transistor amplifier for a hearing aid comprising in combination: a. meanS for deriving from a point in said amplifier an audio frequency voltage whose amplitude is proportional to that of the audio frequency signal at a point along the forward amplification path of the amplifier; b. means for converting said audio frequency voltage into a d.c. control voltage; c. a circuit network including a frequency-dependent circuit comprising a variable resistor and a capacitor connected in parallel in the emitter lead of a transistor of one of the stages for influencing the frequency response of the amplifier in the voice frequency range; and d. means for applying said control voltage to said frequency-dependent circuit, whereby the frequency characteristics of said frequency-dependent circuit are varied in response to changes in the amplitude of said audio frequency voltage.

Claim 14

A multi-stage transistor amplifier for a hearing aid comprising in combination: a. meanS for deriving from a point in said amplifier an audio frequency voltage whose amplitude is proportional to that of the audio frequency signal at a point along the forward amplification path of the amplifier; b. means for converting said audio frequency voltage into a d.c. control voltage; c. a circuit network including a frequency-dependent circuit comprising a variable resistor and a capacitor connected in parallel in the emitter lead of a transistor of one of the stages for influencing the frequency response of the amplifier in the voice frequency range; and d. means for applying said control voltage to said frequency-dependent circuit, whereby the frequency characteristics of said frequency-dependent circuit are varied in response to changes in the amplitude of said audio frequency voltage.