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US 6,549,073 B1Granted
Operational amplifier with common mode gain control using impedance transport
AssigneeXerox Corporation
InventorHarry J. McIntyre
Life of this patent
Estimating the term…
Abstract
A differential amplifier circuit connected to an impedance transport circuit is disclosed. The impedance transport circuit transports an AC input impedance to an output impedance and invert its polarity thereby enabling the common-mode gain of the differential amplifier to be varied. This impedance transport circuit utilizes two MOS transistors and an Op-Amp that causes the drain voltages of the transistors to be equal.
Claims15
A differential amplifier circuit, comprising
- a first metal oxide silicon field effect transistor and a second metal oxide silicon field effect transistor whose sources are differentially connected to each other;
- a constant current source connected to the sources of said first and said second transistor producing a first common impedance;
- a third metal oxide silicon field effect transistor having a first drain voltage;
- a fourth metal oxide silicon field effect transistor having a second drain voltage;
- a second adjustable impedance,
- a first balancing circuit being electrically connected to said third transistor, said fourth transistor and said second adjustable impedance;
- said third and said fourth transistors being responsive to said first balancing circuit for causing said second adjustable impedance to have a polarity opposite said first common impedance wherein varying said second adjustable impedance changes said differential amplifier's circuit's common-mode gain.
4 more elements
A differential amplifier circuit, comprising
- a first NMOS metal oxide silicon field effect transistor and a second NMOS metal oxide silicon field effect transistor whose sources are differentially connected to each other;
- a constant current source connected to the sources of said first and said second transistor producing a first common impedance;
- a third NMOS metal oxide silicon field effect transistor having a first drain voltage;
- a PMOS fourth metal oxide silicon field effect transistor having a second drain voltage;
- a second adjustable impedance,
- a first balancing circuit being electrically connected to said third transistor, said fourth transistor and said second adjustable impedance;
- said third and said fourth transistors being responsive to said first balancing circuit for causing said second adjustable impedance to have a polarity opposite said first common impedance wherein varying said second adjustable impedance changes said differential amplifier's circuit's common-mode gain.
4 more elements
A differential amplifier circuit, comprising
- a first bi-polar transistor and a second bipolar transistor whose emitters are differentially connected to each other;
- a constant current source connected to the emitters of said first and said second bipolar transistor producing a first common impedance;
- a third NMOS metal oxide silicon field effect transistor having a first drain voltage;
- a PMOS fourth metal oxide silicon field effect transistor having a second drain voltage;
- an second adjustable impedance,
- a first balancing circuit being electrically connected to said third transistor, said fourth transistor and said second adjustable impedance;
- said third and said fourth transistors being responsive to said first balancing circuit for causing said second adjustable impedance to have a polarity opposite said first common impedance wherein varying said second adjustable impedance changes said differential amplifier's circuit's common-mode gain.
4 more elements
Dependencies are inferred from the claim text.