Gallium arsenide differential amplifier with closed loop bias stabilization
AssigneeTriQuint Semiconductor, Inc.
InventorM. Louis Pengue, Jr.
Life of this patent
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Abstract
A gallium arsenide differential amplifier is compensated against temperature and process induced variations so as to provide phase and amplitude matched differential output signals centered about an internal GaAs reference voltage. Compensation of the amplifier is effected by one or more current sources which are adjustably responsive to the dynamic common mode level of the output signals. The resultant amplifier provides a high common mode rejection ratio and facilitates implementation of otherwise impracticable differential GaAs circuit topologies.
Claims19
A gallium arsenide (GaAs) differential voltage amplifier, compensated for temperature and process variations, comprising:
- signal input means for inputting an input logic signal;
- signal output means for outputting an output logic signal;
- a common source gallium arsenide field effect transistor (GaAsFET) differential amplifier comprising a pair of common source connected GaAsFETS, each having a drain coupled to a voltage input through a voltage dropping means, each GaAsFET having a gate input and a drain output, said gate inputs being coupled to the signal input means and the drain outputs providing output differential logic signals;
- the GaAsFET differential amplifier further including a current source means connected to the common source of the GaAsFETs for producing current flow through the GaAsFETs and the voltage dropping means, the current source means being adjustably responsive to a signal applied to a control signal input of the current source means to vary said current flow;
- first coupling means for coupling the differential logic signals from the GaAsFET drains to the signal output means;
- sampling means coupled to the GaAsFET drains for generating a true common mode signal from the differential logic signal;
- and
- second coupling means for coupling the true common mode signal to the control signal input of the current source.
A method for compensating a gallium arsenide differential amplifier comprising:
- providing a differential common source amplifier including a pair of common source connected gallium arsenide FETs (GaAsFETs), each having a drain coupled to an input voltage source through a means for dropping voltage, and also having a gate input, the amplifier further including a variable current source connected to said common source of said GaAsFETs and having adjustment means for varying output current through the current source, the GaASFETs and the voltage dropping means;
- applying a logic signal to the GaAsFET gates;
- extracting a pair of differential output signals from the GaAsFET drains;
- deriving a true common mode signal from the differential output signals;
- coupling the true common mode signal back to the adjustment means of the differential amplifier current source;
- and
- varying the output of the current source to minimize variations of the true common mode signal and to maintain phase and amplitude matched differential output signals relative to their common mode level.
Dependencies are inferred from the claim text.