Miscellaneous active electrical nonlinear devices – circuits – and – Specific input to output function – Logarithmic
Patent
1994-08-08
1997-04-29
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific input to output function
Logarithmic
327552, 327560, 330109, 330304, 330305, 330254, H03K 500, H04B 100
Patent
active
056253176
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. The filter frequency accuracy is established by trimming the frequency of the oscillation in test mode during wafer probe or by adjusting the circuit biasing to tune the cutoff frequency in test mode during power-up or between reads in a memory system. The oscillation is disabled during normal operation of the filter.
REFERENCES:
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patent: 5063309 (1991-11-01), Yamasaki
patent: 5200716 (1993-04-01), Amano
patent: 5243239 (1993-09-01), Khan et al.
patent: 5289136 (1994-02-01), De Veirman et al.
patent: 5371425 (1994-12-01), Brown
patent: 5440264 (1995-08-01), Sevenhans et al.
Brady III W. James
Callahan Timothy P.
Donaldson Richard L.
Le Dinh T.
Swayze, Jr. W. Daniel
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