Amplifiers – Signal feedback – In cascade amplifiers
Reexamination Certificate
2008-10-16
2010-10-26
Choe, Henry K (Department: 2817)
Amplifiers
Signal feedback
In cascade amplifiers
C330S278000
Reexamination Certificate
active
07821335
ABSTRACT:
The variable gain amplifier includes a bias circuit (BC)1, a matching circuit (MC)2, a variable gain resistive feedback amplifier (FA)3and an output follower (EA)4. The resistance values of the load resistance Rc and feedback resistance Rf are changed in cooperation. In a case of making the load resistance Rc a high resistance to set the low noise amplifier to a high gain, the feedback resistance Rf is also made a high resistance, the feedback time constant τfb(c1)≈2π·RfCbe/(1+gmRc) of the closed loop of the resistive negative feedback amplifier3becomes substantially constant, and then the amplifier has a gain small in frequency dependency over a wide bandwidth. In a case of making the load resistance Rc a low resistance to set the low noise amplifier to a low gain, the feedback resistance Rf is also made a low resistance. The feedback resistance Rf with the low resistance increases the negative feedback quantity, and thus the amplifier is set to a low gain. Also, the load resistance Rc is made a low resistance, and the feedback time constant τfb(c1) becomes substantially constant. The gain is not lowered further in a high frequency region.
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Shiramizu et al. “A 3-10 GHz Bandwidth Low-Noise and Low-Power Amplifier for Full-Band UWB Communications in 0.25-μm SiGe BiCMOS Technology” 2005 IEEE Radio Frequency Integrated Circuits Symposium, pp. 39-42.
Garuda et al., “A-3-5 GHz Fully Differential CMOS LNA with Dual gain mode for Wireless UWB Applications”, 2005, 48thMidwest Symposium on Circuits and Systems, Vol. 1, pp. 790-793, 7-10, Aug. 2005.
Masuda Toru
Shiramizu Nobuhiro
Choe Henry K
Miles & Stockbridge P.C.
Renesas Electronics Corporation
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