Stability and enhanced gain of amplifiers using inductive coupling
OwnerJames Burr Hechtinventor
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Abstract
The present invention improves the stability and enhances the gain of amplifiers, particularly transistor amplifiers, by using mutual inductive coupling to partially cancel feedback current. Inductors at the input and output of an amplifier are positioned so that a mutual inductance is created between the two inductors. The mutual inductance is used to cancel the inherent capacitive feedback of transistor amplifiers. The use of mutually coupled inductors allows a large value of effective inductance to be obtained by using relatively small inductors. The use of mutually coupled inductors also avoids the problem of low-frequency instability.
Claims33
A telephone handset for communicating with a base station, the handset generating and amplifying signals to be transmitted to the base station, the handset comprising:
- an amplifier for boosting the gain of the signals prior to transmission, the amplifier having capacitive feedback between an input and an output of the transistor wherein a mutual inductance neutralizes the amplifier, the amplifier comprising:
- a transistor having an input terminal and an output terminal;
- a first inductor coupled to the input terminal of the transistor;
- and
- a second inductor coupled to the output terminal of the transistor, wherein the first inductor and the second inductor are positioned relative to each other to create the mutual inductance between the output terminal of the transistor and the input terminal of the transistor, the mutual inductance resonating with the feedback capacitance in the transistor and wherein the amplifier, the first inductor, and the second inductor are implemented on an integrated circuit without the use of discrete components.
An apparatus comprising:
- an amplifier having an input terminal and an output terminal;
- a first inductor coupled to the input terminal of the amplifier;
- and
- a second inductor coupled to the output terminal of the amplifier, wherein the first inductor and the second inductor are positioned relative to each other to create a mutual inductance which cancels at least a portion of feedback in the amplifier.
A method of reducing feedback in an amplifier comprising the acts of:
- coupling a first inductor to an input terminal of the amplifier;
- coupling a second inductor to an output terminal of the amplifier;
- and
- positioning the first inductor and the second inductor relative to each other to create a mutual inductance which cancels at least a portion of the feedback in the amplifier.
An apparatus comprising:
- means for amplifying a signal having an input and an output;
- first inductive means coupled to the input of the amplifying means;
- and
- second inductive means coupled to the output of the amplifying means, wherein the first inductive means and the second inductive means are positioned relative to each other to create a mutual inductance between the output of the amplifying means and the input of the amplifying means, the mutual inductance neutralizing the amplifying means.
Dependencies are inferred from the claim text.