Amplifiers – With semiconductor amplifying device – Including balanced to unbalanced circuits and vice versa
Reexamination Certificate
2001-09-04
2003-05-06
Callahan, Timothy P. (Department: 2816)
Amplifiers
With semiconductor amplifying device
Including balanced to unbalanced circuits and vice versa
C330S253000, C330S300000, C330S310000
Reexamination Certificate
active
06559723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to wide band linear amplifiers and more particularly to resistively loaded wide-band high frequency linear amplifiers with a single ended input and a differential output.
2. Background Description
Wide band multi-channel communication systems require wide band amplifiers with a high degree of linearity to avoid second and third order affects arising from a large number of potential carrier interactions. Traditional wide band amplifiers require very expensive external tracking filters, e.g., an external balun. Thus, because differential circuits and in particular differential circuits with external baluns minimize second and third order effects, they are used, overwhelmingly, in high performance narrow band applications to maximize amplification linearity.
For many applications an external balun or other tracking filter is prohibitively expensive and, an on-chip single ended (single phased) input to differential (output) converter is necessary to maintain acceptable linearity and dynamic range. Prior single ended to differential conversion approaches have resulted in circuits, typically bipolar, with limited dynamic operating range and still some sensitivity to second and third order effects especially at the extremes of that operating range, as well as device noise sensitivity, e.g. from device mismatches. While second and third order effects could be further reduced, that reduction was at a cost of even further limiting amplifier dynamic operating range.
Further, these single ended to differential bipolar amplifiers do not lend themselves to a field effect transistor (FET) analog. In particular, FET thresholds vary disproportionately for low back gate bias voltages (i.e., the voltage between the device channel and the bulk substrate) such that, because of bias conditions, identical devices may have different thresholds. So, threshold voltages for two matched FETs may exhibit a significant mismatch which reduces linearity. Thus, even if devices are identical by design, device configuration and bias voltages may be mismatched to cause a transconductance mismatch, severely degrading operation of such an FET amplifier.
Thus, there is a need for a single ended input to differential output linear amplifier with a wide dynamic operating range, improved gain and minimal second and third order effect degradation.
REFERENCES:
patent: 5065043 (1991-11-01), Bartling et al.
patent: 5497123 (1996-03-01), Main et al.
patent: 5767662 (1998-06-01), Perkins
patent: 5946878 (1999-09-01), Grund et al.
patent: 6150881 (2000-11-01), Lovelace et al.
Connell Lawrence Edwin
Hollenbeck Neal W.
Callahan Timothy P.
Meyer Jonathan P.
Motorola Inc.
Nguyen Linh
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