Amplifiers – With semiconductor amplifying device – Including distributed parameter-type coupling
Reexamination Certificate
2001-12-31
2003-01-07
Pascal, Robert (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including distributed parameter-type coupling
C330S302000
Reexamination Certificate
active
06504434
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a method for configuring low-noise integrated amplifier circuits.
To use prior art integrated low-noise amplifiers, the user has to develop a matching circuit that optimally matches the input impedance of the low-noise amplifier to the output impedance of the preceding stage or of the preceding transfer element. Such a configuration minimizes the reflection of the power at the input of the low-noise amplifier.
Respective &pgr; equivalent circuit diagrams of a bipolar transistor are specified on pages 36 and 39 of the document Gray, Paul “Analysis and Design of Analog Integrated Circuits”. The calculation of the noise properties of such a transistor is explained on page 776 et seq.
The document “Theoretische Grenzen für Anpassungsnetzwerke in optischen Empfängern (Teil II)” [Theoretical Limits for Matching Networks in Optical Receivers (Part II)], A. Czylwik, Frequenz, Vol. 49, No. 3/04, pages 58 to 65, specifies a method for power and noise matching of a field-effect transistor to a photodiode.
Depending on the noise properties of the amplifier, however, it has not been possible to ensure that the noise figure of the amplifier is less than a predetermined value for the noise figure.
Moreover, the realization and dimensioning of the matching circuit by external components means an additional outlay with respect to the circuitry of the integrated low-noise amplifier.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for configuring low-noise integrated amplifier circuits that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that requires no additional external circuitry when using the amplifier circuit.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for producing a low-noise integrated amplifier circuit including the steps of providing an integrated amplifier circuit having an input stage with one of the group consisting of a common-emitter bipolar transistor and a common-source field-effect transistor, each transistor having a collector with an effective load, the amplifier circuit having an input impedance, a noise figure, and integrated components with component values, connecting a transfer element upstream with respect to the amplifier circuit, the transfer element having a predetermined output impedance with a real part, and dimensioning the amplifier circuit by (a) noise matching the amplifier circuit to the real part of the predetermined output impedance of the transfer element by determining a range of resistances in which the noise figure of the amplifier circuit is less than a predetermined noise figure by at least one of the group consisting of first defining process parameters during the production of the amplifier circuit, first defining geometry parameters of at least one of the integrated components of the amplifier circuit, a dimensioning of the component values, and first defining one of a collector current and a drain current, the noise figure of the amplifier circuit being dependent on a real generator resistance, and by determining a value of the real part of the predetermined output impedance lying in the range, and, for the first definition of the parameters of the amplifier circuit, determining a minimum noise figure and an associated optimum generator resistance and realizing the amplifier circuit with the associated parameters if the minimum noise figure is less than or equal to the predetermined noise figure and the optimum generator resistance corresponds, within predetermined tolerances, to the real part of the predetermined output impedance, otherwise performing a new definition of the parameters, replacing the first definition, with other parameters deviating from the first definition, and (b) subsequently, power matching the input impedance of the amplifier circuit to the predetermined output impedance by selecting the effective load on the collector of the transistor to produce a complex voltage gain generating, due to the Miller effect, an input impedance equal to a complex conjugate of the predetermined output impedance.
The invention is based on the insight that, by the definition of different parameters (such as process parameters during the production of the integrated low-noise amplifier and/or geometry parameters of one or more components of the amplifier and/or component values of the amplifier and/or the collector current or the drain current) “noise matching” to a predetermined output impedance of a preceding transfer element can be achieved when the parameters are chosen such that the noise figure F(R
G
) of the amplifier (the noise figure being dependent on the real part of a complex generator impedance) is less than a predetermined desired value Fdesired for the noise figure in a range in which the real part of the predetermined output impedance of an arbitrary transfer element connected upstream of the amplifier also lies. Strictly speaking, genuine noise matching would be given only when the value of the real generator resistance, at the minimum of the profile of the noise figure of the amplifier as a function of the real generator resistance, corresponds to the real part of the output impedance of the preceding transfer element. The following description will address noise matching even when such a condition is only approximately satisfied.
If the above-mentioned parameters are chosen to give noise matching, then, according to the invention, the effective load on the collector or the drain of the transistor of the input stage of the amplifier is chosen to produce an amplifier input impedance that is substantially equal to the complex conjugate of the output impedance of the preceding transfer element. For example, power matching is performed by the choice of the load. In such a case, the invention exploits the Miller effect, according to which the collector-base capacitance or the drain-gate capacitance that is multiplied by the voltage gain, in the emitter circuit of a bipolar transistor or in the source circuit of a field-effect transistor, concomitantly determines the input capacitance of the amplifier circuit.
Because the voltage gain is generally a complex quantity that only depends on the (complex) load on the collector or the drain of the transistor of the input stage and, if appropriate, on the inductance (or the impedance) at the emitter or the source, the input impedance is able not only to be altered in terms of magnitude but also to be rotated within certain limits in the complex plane so that, by the suitable choice of the load in (nevertheless relatively wide) limits, the input impedance of the amplifier can be determined such that it corresponds to the complex conjugate of the output impedance of the preceding transfer element.
The intensity of the Miller effect has practically no influence on the input-related noise sources in the noise equivalent circuit diagram of the amplifier circuit. In other words, the noise matching and the power matching can be performed substantially independently of one another by the method according to the invention.
According to an embodiment of the method according to the invention, the noise matching is performed in a first step and the power matching is performed in a subsequent second step. Such a procedure has the advantage of lower complexity because a plurality of quantities have to be taken into account in the noise matching and the power matching can be effected only by a corresponding choice of the load as single quantity.
According to another embodiment of the method according to the invention, firstly a set (that preferably appears expedient) of the crucial parameters are chosen for noise matching. With these parameters, the minimum noise figure F
opt
and the associated optimum real generator resistance R
opt
are then determined. The determination can be effected, of course, using simplified approximation relationships
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Nguyen Khanh Van
Pascal Robert
LandOfFree
Method for configuring low-noise integrated amplifier circuits does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for configuring low-noise integrated amplifier circuits, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for configuring low-noise integrated amplifier circuits will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3059684