RADIO FREQUENCY PEAK DETECTION WITH SUBTHRESHOLD BIASING
First Claim
1. A circuit comprising:
- a load capacitor;
a first and a second field effect transistor, each transistor having a channel and a gate, the gate of the first transistor being coupled to a first input node and the gate of the second transistor being coupled to a second input node, the channels of the first and second field effect transistors being arranged in parallel with the load capacitor;
a first current source operative to charge the load capacitor and to set a bias current for the field effect transistors;
a low-pass filter connected between the load capacitor and an output node; and
a biasing circuit connected to the gates of the first and second transistors, the biasing circuit being operative to provide a biasing voltage lower than a threshold voltage of the first and second transistors.
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Accused Products
Abstract
A radio-frequency peak amplitude detection circuit includes a load capacitor, a current source that charges the load capacitor and set the bias current for the field effect transistors, and a pair of field effect transistors. The gates of the field effect transistors are biased at a level below the threshold voltage of the transistors. The transistors are arranged in parallel with the capacitor and are operable to drain the capacitor at a rate determined by a differential input at the gates of the transistors. The voltage across the load capacitor is low-pass filtered and has a voltage level representative of the amplitude of the differential input signal.
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Citations
20 Claims
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1. A circuit comprising:
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a load capacitor; a first and a second field effect transistor, each transistor having a channel and a gate, the gate of the first transistor being coupled to a first input node and the gate of the second transistor being coupled to a second input node, the channels of the first and second field effect transistors being arranged in parallel with the load capacitor; a first current source operative to charge the load capacitor and to set a bias current for the field effect transistors; a low-pass filter connected between the load capacitor and an output node; and a biasing circuit connected to the gates of the first and second transistors, the biasing circuit being operative to provide a biasing voltage lower than a threshold voltage of the first and second transistors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A circuit comprising:
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a peak detection circuit including a first and a second field effect transistor, each transistor having a gate coupled to a respective input node; a biasing circuit having a bias output node connected to the gates of the first and second transistors, the biasing circuit being operative to provide a biasing voltage lower than a threshold voltage of the first and second transistors, the biasing circuit further comprising; a third and a fourth field effect transistor, each transistor having a channel and a gate, the gates of the third and fourth field effect transistors being connected to the bias output node; a current source operative to supply a current to the channels of the third and fourth transistors; and a comparator circuit operative to apply a voltage to the bias output node, the comparator circuit being responsive to a voltage level across the channels of the third and fourth transistors. - View Dependent Claims (14, 15)
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16. A method comprising:
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charging a load capacitor; discharging the load capacitor through a first channel of a first field effect transistor and a second channel of a second field effect transistor; biasing a gate of the first field effect transistor and a gate of the second field effect transistor at a bias voltage below a threshold voltage of the first field effect transistor and the second field effect transistor; applying a differential input signal at the gate of the first field effect transistor and the gate of the second field effect transistor; and low-pass filtering a voltage across the load capacitor to generate an output signal. - View Dependent Claims (17, 18, 19, 20)
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Specification