Amplitude-adjustable oscillator
AssigneeSequoia Communications
InventorsJohn Groe, Joseph Austin
Life of this patent
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Abstract
Amplitude-adjustable oscillator. The oscillator includes a feedback loop to control the amplitude of an oscillator output signal. The feedback loop includes a pair of clamping transistors, wherein base terminals of the clamping transistors are coupled to an adjustable voltage signal to prevent saturation of the oscillator circuit. The feedback loop also includes a filter to monitor the current flowing through the clamping transistors. The feedback loop also includes an amplifier to compare an output of the clamping transistors to a reference signal, and a reference generator to set an operating bias for the oscillator.
Claims9
A feedback loop for use with a differential direct-coupled oscillator circuit to control the amplitude of an oscillator output signal, the feedback loop comprising:
- a pair of clamping transistors, wherein base terminals of the clamping transistors are coupled to an adjustable voltage signal to prevent saturation of the oscillator circuit;
- a filter to monitor the current flowing through the clamping transistors;
- an amplifier to compare an output of the clamping transistors to a reference signal;
- and
- a reference generator to set an operating bias for the direct-coupled oscillator.
A feedback circuit for use with a differential direct-coupled oscillator circuit to control the amplitude of an oscillator output signal, the feedback loop comprising:
- a detector circuit having a detector input coupled to the oscillator circuit and a detector output;
- a current amplifier circuit having a first amplifier input coupled to the detector output, and having an amplifier output;
- and
- a bias generator having a bias input coupled to the amplifier output and a bias output coupled to the oscillator circuit.
A method for controlling the output amplitude of a differential direct-coupled oscillator, the method comprising steps of:
- clamping a low peak of an output signal of the oscillator;
- monitoring a clamping current;
- converting the clamping current to a filtered voltage;
- comparing the filtered voltage to a reference voltage to produce a difference voltage;
- and
- setting a bias current in the oscillator using the difference voltage.
Dependencies are inferred from the claim text.