Multiple input, fully differential, wide common-mode,...

Details Multiple input, fully differential, wide common-mode,... Multiple input, fully differential, wide common-mode,...

2001-06-28

2003-09-30

Shingleton, Michael B (Department: 2817)

Amplifiers

With semiconductor amplifying device

Including differential amplifier

C330S257000, C330S261000

Reexamination Certificate

active

06628168

ABSTRACT:

FIELD
Embodiments of the present invention relate to analog circuits, and more particularly, to analog amplifier circuits with multiple inputs.
BACKGROUND
Differential amplifiers are ubiquitous building blocks in many analog systems. Many applications require linear amplification of multiple differential input voltages by a single amplifier, where addition and subtraction are some of the general functions performed on the multiple input voltages. Such summing and differencing functions find applications in analog filters and bi-directional signaling receivers, to name just a couple.
A prior art differential amplifier circuit for two differential input voltages is shown in FIG.
1
. Input ports
102
A and
102
B comprise a first differential input port pair for receiving a first differential input voltage, and input ports
104
A and
104
B comprise a second differential input port pair for receiving a second differential input voltage. A differential output voltage is provided by output ports
106
A and
106
B.
Transistors
102
A and
102
B are nMOSFETs (Metal Oxide Semiconductor Field Effect Transistor) comprising a first differential pair, and nMOSFETs
104
A and
104
B comprise a second differential pair. Current sink
108
sinks bias currents from nMOSFETs
102
A and
102
B, and current sink
110
sinks bias currents from nMOSFETs
104
A and
104
B. A load
112
is connected to the drains of nMOSFETs
102
A and
104
A, and load
114
is connected to the drains of nMOSFETs
102
B and
104
B. These loads may be active loads.
The circuit of
FIG. 1
may easily be generalized to an arbitrary number of differential input port pairs, and may be used for performing summation or differencing. However, for demanding applications the circuit of
FIG. 1
may suffer from limited input common mode voltage range, limited common mode rejection, and low gain.


REFERENCES:
patent: 5745007 (1998-04-01), Redman-White
patent: 6043708 (2000-03-01), Barr
Roewer Et Al. “A Novel Class of Complementary Folded-Cascode Opamps for Low Voltage” IEEE Journal of Solid-State Circuits vol. 37 Issue of 8 Aug. 2002 pp 1080-1083.*
W. Dally and J. Poulton, Cambridge University Press, Digital Systems Engineering, 1998, p. 369.
IEEE Journal Of Solid State Control Circuits, vol. 26, No. 2, Feb. 1991, Two Novel Fully Complementary Self Biased CMOS Differential Amplifiers, pp. 165-168.

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