Phase locked loop circuitry with variable gain and bandwidth

Details Phase locked loop circuitry with variable gain and bandwidth Phase locked loop circuitry with variable gain and bandwidth

1993-06-24

1994-07-26

Sikes, William L.

Electrical transmission or interconnection systems

Nonlinear reactor systems

Parametrons

307264, 307268, 328155, H03L 716, H03L 708

Patent

active

053329309

ABSTRACT:
An adjustable current source circuit of a phase locked loop (PLL) circuitry fabricated on a single substrate provides a first current that is a function of an error voltage proportional to an amount of a phase difference of a comparison of a reference signal and a feedback signal. The circuit includes a first current source coupled to receive a second current from a reference phase locked loop of the PLL circuitry for providing a first portion of the first current under control of the second current. The first portion of the first current is proportional to the second current. A second current source is coupled to receive a third current from a transconductance amplifier of the PLL circuitry for providing a second portion of the first current under control of the third current. The second portion of the first current is proportional to the third current. A third current source provides a third portion of the first current selectively proportional to one of the second and third currents. A switching circuit is coupled to receive the second and third currents for selectively controlling the third current source to couple to one of the second and third currents in order to cause the third portion of the first current proportional to the selected one of the second and third currents such that the first current can be switched to have one of a first current ratio and a second current ratio between the second and third currents and therefore the PLL circuitry can be switched between a first and a second bandwidth and loop gain.

REFERENCES:
patent: 4316150 (1982-02-01), Crosby
patent: 4668918 (1987-05-01), Adams
patent: 4686481 (1987-08-01), Adams
patent: 4819081 (1989-04-01), Volk et al.
patent: 4829258 (1989-05-01), Volk et al.

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