AMPLITUDE MODULATED RF GENERATOR FOR QUADRUPOLE MASS ANALYZER

• US 3,621,464 A
• Filed: 11/20/1969
• Issued: 11/16/1971
• Est. Priority Date: 11/20/1969
• Status: Expired due to Term

• Current Assignee: Fonger Wiersma, Robert M. Bryndza
• Original Assignee: Fonger Wiersma, Robert M. Bryndza
• Inventors: Robert, M. Bryndza, Wiersma, Fonger
• Primary Examiner(s): Roy Lake
• Assistant Examiner(s): Siegfried H. Grimm
• Application Number:
  US04/878,315
• Time in Patent Office: 726 Days
• Field of Search: 331/106,109,182,183 250/41.9DS
• US Class Current: 331/106
• CPC Class Codes: H01J 49/022 Circuit arrangements, e.g. for generating deviation currents or voltages regulating electric or magnetic variables in general, e.g. current, magnetic field G05F; Components associated with high voltage supply high voltage supply per se H02M
• CPC Class Codes: H01J 49/421 Mass filters, i.e. deviating unwanted ions without trapping
• CPC Class Codes: H03L 5/00 Automatic control of voltage, current, or power

Abstract

An improved radio frequency (RF) generator for use with a quadrupole mass analyzer is disclosed wherein a ramp of RF at constant frequency is provided by developing a difference signal between the output of the circuit and a control ramp input. The error signal is modulated by the desired frequency supplied from an oscillator and amplified by a push-pull arrangement. The amplified signal is applied to a series resonant tuned circuit which directly supplies the quadrupole rods.

Claims

1. A radiofrequency generator for supplying a variable amplitude radiofrequency electrical energy comprising:

an oscillator for producing a constant frequency output signal;

switch means connected to said oscillator and responsive to said output signal, said switch means being rendered alternately conductive and nonconductive at said frequency;

first amplifier means connected to said switch means, a series resonant circuit connected to said amplifier for producing an output voltage having a magnitude dependent upon the output of said first amplifier, detector means connected to said tuned circuit for producing an electrical signal representing said output voltage;

means for producing a ramp voltage;

differential amplifier means having a first input connected to receive said ramp voltage and a second input connected to said detector means for producing an output signal representing the amplitude difference between said ramp and said output voltage;

means including second amplifier means connected to said differential amplifier and to said switch means for applying said difference signal to said switch means and said first amplifier means whereby the magnitude of said resonant circuit output voltage is a function of said difference signal at said oscillator frequency.

2. A radiofrequency generator comprising:

means for producing a control signal having a predetermined frequency, a resonant circuit for supplying a constant frequency output voltage having variable amplitude, means for producing a voltage having a predetermined amplitude change;

means connected to said voltage producing means and to said resonant circuit for producing a difference signal representing the difference in amplitude between said variable amplitude radiofrequency voltage and said source;

means including switch means connected to said control signal producing means;

to said resonant circuit; and

to said difference signal producing means for selectively applying said difference signal to said resonant circuit at said predetermined frequency;

whereby the frequency of said output voltage is said predetermined frequency and the amplitude of said output voltage tracks said predetermined amplitude change.