With Vacuum Tube Patents (Class 327/353)
  • Patent number: 5625317
    Abstract: A high-frequency integrated continuous-time filter with built-in test mode. The present invention provides the ability to easily track the cutoff frequency of the filter without the additional power and area requirements and noise sources present in prior art master/slave tuning schemes. Furthermore, the filter being tested is the actual filter that is used to process signals, unlike the prior art where a similar but separate filter or oscillator is used to tune the bias values for both circuits. Better tuning accuracy is thus obtained in the present invention. The circuit is designed to oscillate in test mode at the cutoff frequency of the filter. Oscillation is achieved by moving the poles of the filter from the left half-plane either onto the imaginary axis or into the right half-plane.
    Type: Grant
    Filed: August 8, 1994
    Date of Patent: April 29, 1997
    Assignee: Texas Instruments Incorporated
    Inventor: Geert Deveirman