RFIC_Lecture_Note_No12_p202-p216 (Low Noise Amplifiers)

RFIC_Lecture_Note_No12_p202-p216 (Low Noise Amplifiers) -...

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ECE695F RFIC Prof. S. Mohammadi Low Noise Amplifiers Example An NMOS transistor has been measured at 4 GHz under the () mA I V V D DS 4 , 5 . 2 = = bias condition ° = 169 552 . 0 11 S ° = 23 049 . 0 12 S ° = 26 681 . 1 21 S ° = 67 839 . 0 22 S measured S-parms dB F 5 . 2 min = ° = Γ 166 475 . 0 opt = 5 . 3 n R measured noise characteristics Design a low-noise amplifier with minimum noise figure Step 1: determine the stability (we only have one point (4 GHz) ? ) 1 01 . 1 2 1 12 21 2 2 22 2 11 > = + = S S S S k 1 111 419 . 0 21 12 22 11 < = = o S S S S transistor is unconditionally stable at 4 GHz ( ) dB k k S S MAG 7 . 14 1 2 12 21 = = matching condition for achieving MAG o o 70 98 . 0 , 154 94 . 0 = Γ = Γ oft L oft S output matching to achieve highest possible gain input matching to achieve highest possible gain - - 202
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ECE695F RFIC Prof. S. Mohammadi but F min is obtained at o 166 475 . 0 = Γ = Γ opt S 1 j 1 j dB F 5 . 2 min = to get higher gain dB MAG 7 . 14 = 2 2 21 2 11 2 1 1 1 1 out S S A S S G Γ Γ Γ = ° = Γ Γ + = Γ 70 844 . 0 1 11 21 12 22 S S out S S S S substitute o 166 475 . 0 = Γ = Γ opt S you can calculate G A dB G A 7 . 10 = 4 dB gain degradation Since R n is small in this case, it could be better if you deviate from to get higher gain opt Γ never the less, let s stick to opt S Γ = Γ now to get maximum gain you need ° = Γ = Γ 70 844 . 0 * out L therefore ° = Γ Γ + = Γ Γ 157 744 . 0 1 22 21 12 11 S S S S L in - - 203
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ECE695F RFIC Prof. S. Mohammadi All you need to do is to design the matching network to show o 166 475 . 0 = Γ S o 70 844 . 0 = Γ L at 4 GHz either use transmission lines or passive components (L & C) to design the matching network. Why?
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RFIC_Lecture_Note_No12_p202-p216 (Low Noise Amplifiers) -...

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