Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2008-05-19
2009-11-03
Nguyen, Patricia (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S302000, C327S111000
Reexamination Certificate
active
07612609
ABSTRACT:
A circuit for providing a self-stabilizing, differential load circuit with well controlled complex impedance to an amplifier is described. According to an embodiment, two pairs of transistors in a cross-coupled configuration, a degeneration resistor for each transistor, and parasitic capacitance cancelation capacitors provide a self-stabilizing, differential load. Small signal analysis of the circuit illustrates an impedance of the load circuit to be substantially equal to a combination of impedance values with substantially little dependence on transconductances and incremental resistances of the transistors over an extended frequency range. By employing well matched resistors, impedance of the load to the amplifier can be controlled and common mode feedback loops avoided, because a current source is not employed as a load. The use of parasitic capacitance cancelation capacitors can substantially increase the bandwidth of the amplifier. Furthermore, with transistors, low voltage headroom may be increased and integrated circuit area decreased.
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Darby & Darby P.C.
Gaffney Matthew M.
National Semiconductor Corporation
Nguyen Patricia
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