US 4,283,691 A · Crystal oscillator having low noise signal extraction circuit

Abstract

A method and apparatus for minimizing the noise component of the output signal from a resonator oscillator. A single transistor or Darlington pair of transistors in the common base configuration is placed in series with the crystal resonator of the oscillator with a selected output load impedance connected between the base and collector of the transistors. By making use of this configuration, it is possible to use the crystal resonator as an initial filter to minimize the noise component of the output signal contributed by the oscillator loop as well as minimizing the inherent noise component from the output buffer amplifiers in the output signal. A common base configuration of both of these embodiments provides a low impedance load on the oscillator loop thus minimizing the effect on tuning or Q of the oscillator while making it possible to select an output impedance load that is of sufficient size to present an output signal having a sufficiently high signal to noise ratio to provide the minimization sought.

Claims9

Dependent claims

A resonator oscillator with signal extraction apparatus to minimize the noise power component of the output signal from the oscillator, said oscillator comprising:

oscillator loop means including:
inverting amplifier means having an input terminal and an output terminal;
signal feedback means including:
crystal resonator means having a current flowing therethrough and having a first end coupled to the input terminal of the inverting amplifier means, and having a second end coupled to the output terminal of the inverting amplifier;
and
first and second shunt reactive means, said first shunt reactive means having one end connected to the input terminal of the inverting amplifier means, and said second shunt reactive means having one end connected to the output terminal of the inverting amplifier means, with the other ends of each of said first and second shunt reactive means being connected one to the other;
and
active output means being connected in series with the crystal resonator means with the current flowing through this means being the current that flows through said crystal resonator means for presenting a low impedance to the oscillator loop, and generating a high signal to noise ratio output signal in response to the crystal resonator current.

5 more elements

Dependencies are inferred from the claim text.

Crystal oscillator having low noise signal extraction circuit

Life of this patent

Crystal oscillator having low noise signal extraction circuit

Life of this patent

Abstract

Claims9