Low noise transconductance device

Details Low noise transconductance device Low noise transconductance device

2000-02-24

2001-09-18

Lam, Tuan T. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Converting input voltage to output current or vice versa

C327S563000

Reexamination Certificate

active

06292034

ABSTRACT:

FIELD OF THE INVENTION
A low noise transconductance device and especially a low noise amplifier.
BACKGROUND OF THE INVENTION
Transcoductance devices and elements, such as transistors, are vastly used in modern electrical devices. MOS transistors can be found in almost every modern electronic device. Many transcoductance elements are used as amplifiers, and are adapted to receive a signal having a voltage level of Vin and generate an amplified output signal having a current level of Iout, Iout=Gm*Vin, Gm being the transcoductance of the device.
Amplifiers, and almost all known electrical circuits that have a resistive component generate an internal noise also referred to as thermal noise. This unwanted noise is random in nature and generally limits the amplifier performance. Noise is one of the major factors in a signal receiver or amplifier which limits the minimum detectable signal and thereby the information handling capacity of the apparatus. It is desirable, and in some cases critically so, that an amplifier and/or a transcoductance device generates a minimal degree of noise.
One of the methods for minimizing noise of amplifiers is matching a resistance of a signal source and an amplifier. U.S. Pat. No. 4,264,871 of Forward describes a circuit that has a source of electrical signals, being characterized by an inherent source resistance R.sub.S; an amplifier having an input port, an output port, and an internal noise represented by an equivalent input noise voltage V.sub.N, an equivalent input noise current I.sub.N, and an equivalent input noise resistance R.sub.N; and coupling means for matching said source to said amplifier to obtain optimum noise performance, said coupling means having a simulated resistance of: A=−V.sub.N R.sub.S/(V.sub.N −R.sub.S I.sub.N), such that the source resistance R.sub.S is matched to the noise resistance R.sub.N.
A drawback of this method is that it does not try to diminish the noise generated by the amplifier but rather matches the noise to the signal source.
There is a need to provide an improved low noise amplifier and a low noise transcoductance device.


REFERENCES:
patent: 4264871 (1981-04-01), Forward
patent: 5552729 (1996-09-01), Deguchi
patent: 6005431 (1999-12-01), Mehr et al.
patent: 6101561 (2000-08-01), Beers et al.
patent: 6134473 (2000-10-01), Hemming et al.
patent: 6163287 (2000-02-01), Huang
patent: 6166592 (2000-12-01), Walden

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