Amplifiers – Hum or noise or distortion bucking introduced into signal...
Reexamination Certificate
1999-06-30
2001-01-09
Shingleton, Michael B (Department: 2817)
Amplifiers
Hum or noise or distortion bucking introduced into signal...
C330S165000, C330S296000
Reexamination Certificate
active
06172563
ABSTRACT:
BACKGROUND OF THE INVENTION
The lossless-feedback transistor amplifier has been recognized as one of the more effective innovations in small-signal amplifier design. With its ability to deliver both low noise and high linearity response with a minimum amount of effort and cost, both being highly desirable characteristics in small-signal amplifier design, the lossless-feedback amplifier has enjoyed a wide range of applications in communications receiver and radio astronomy telescope receiver design. In a conventional lossless-feedback transistor amplifier, as shown in
FIG. 1
, the amplifier basically consists of a common-base amplifying transistor
105
and a feedback transformer
103
. Generally, the design concept relies on the input impedance of the transistor, seen at the emitter, as being negligible. However, the finite nonlinear input resistance seen at the emitter degrades the expected performance, and the nonlinear nature of this resistance is the primary cause of both harmonic and intermodulation (IM) distortion. Traditional design techniques reduce this nonlinear resistance by increasing the transistor bias current, which produces a limited degree of improvement but which also reduces the overall power efficiency of the amplifier, which is undesirable. It is a desirable design goal to improve the linearity of amplifiers in general without incurring an increase in power consumption.
SUMMARY OF THE INVENTION
An augmented lossless-feedback transistor amplifier circuit with improved intermodulation (IM) performance is described which includes an augmented common base transistor amplifier. The augmented common-base transistor amplifier circuit further includes an augmentation circuit which detects an error voltage at the emitter of the common-base transistor, and which then inverts and amplifies the detected error voltage as a voltage to be applied at the base of the common-base transistor, thereby reducing the error voltage at the emitter of the common-base transistor and in turn improving the linearity and IM performance of the lossless-feedback transistor amplifier circuit. In a further embodiment the augmentation is accomplished by the addition of a common-emitter amplifier circuit. In a further embodiment suitable for higher frequency and lower noise applications, a transformer is used to perform the augmentation. In a further embodiment suitable for high dynamic-range applications, a positive feedback amplifier is used to perform the augmentation. In a further embodiment also suitable for higher dynamic-range applications, a complementary pair of augmented common-base transistors is used in place of the single-ended augmented common-base transistor.
REFERENCES:
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patent: 3891934 (1975-06-01), Norton et al.
patent: 4590434 (1986-05-01), Wagner
patent: 4928072 (1990-05-01), Scott
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Abrahim, E.P. and Y.M. Bruk, and A.A. Kowovalehko, “Highly Linear Broadband Amplifiers with Lossless Feedback, Part 2: Experience and Development, ” International Journal of Electronics, vol. 69, No. 3, pp. 345-357.
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Davis, E.M., “Comparisons Between Multiple Loop and Single Loop Transfer Feedback Amplifiers,” Westoh Convention Record, 1958, vol. 2, Pt. 2, pp. 78-86.
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Morton, D.E., “High Dynamic Range Transistor Amplifiers with Lossless Feedback,” Proceedings of the 1975 IEEE International Symposium on Circuits and Systems, pp. 438-440.
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