Impedance matched variable gain low noise amplifier using shunt feed-back
First Claim
Patent Images
1. An amplifier, comprising:
- a forward amplifier having an input and an output;
a feedback path coupled across said input and output, including, a feedback amplifier coupled to an impedance; and
wherein a signal output of said feedback amplifier is shunted to ground for low gain applications.
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Abstract
The variable gain amplifier includes a forward path that provides the amplifier variable gain, and a feedback path. The feedback path uses a switch that is turned on at low gain levels. The switch taps into the feedback resistor, shunting it to signal-ground and eliminating the feedback mechanism. This ensures that the input impedance seen at the input port does not grow excessively, using part of the feedback resistor as a passive termination at low gain levels. In this way variable gain ranges in excess of 30 dB can be achieved.
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Citations
15 Claims
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1. An amplifier, comprising:
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a forward amplifier having an input and an output;
a feedback path coupled across said input and output, including, a feedback amplifier coupled to an impedance; and
wherein a signal output of said feedback amplifier is shunted to ground for low gain applications. - View Dependent Claims (2, 3, 4)
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5. A variable gain differential amplifier, comprising:
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a differential forward amplifier having a differential input and a differential output; and
a differential feedback path coupled across said differential input and said differential output;
wherein said differential feedback path is shorted together for low gain applications. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of variably amplifying a differential input signal, comprising:
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receiving a differential input signal at an input terminal;
variably amplifying the differential input signal to produce a differential amplified signal at an output;
feeding back a portion of the differential amplified signal through a feedback path that is coupled to the input terminal to produce a differential feedback signal; and
shorting together components of the differential feedback signal for low gain applications.
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Specification