Low-Noise Amplifiers

Transcription

1 007/Oct 4, 31 1

2 General Considerations Noise Figure Low-Noise Amplifiers Table 6.1 Typical LNA characteristics in heterodyne systems. NF IIP 3 db 10 dbm Gain 15 db Input and Output Impedance 50 Ω Input and Output eturn Loss 15 db everse Isolation 0 db tability Factor > 1 noise N figure = N in out

3 Low-Noise Amplifiers General Considerations Noise Figure NF total = 1 ( NF 1 1) NF A 1 p;1 NF3 1 A A p;1 p; L A p;1 NFm 1 L A p;( m 1) in, min L = db Duplexer LNA L NF = db NF total = ~ 4dB P = 174 dbm/hz NF 10log B N E.g. N = 8dB is required, BW = 00kHz, and if NFtotal is about 4dB, the input sensitivity reachable is thus: -109 dbm min 3

4 Low-Noise Amplifiers General Considerations Noise Figure Input-eferred Noise V V n V in Noisy Circuit Vout V in P I n Z in Noiseless Circuit V out N in α V = α in V V NF = ( V n V I n ) For a N voltage out = gain A v from v in P to [ ] V V I ) α A α A V ( n n v Vout : ( V = 1 V = A n,out n I V n 1 4kT ) 4

5 Low-Noise Amplifiers General Considerations Noise Figure V n,rb r b eq V in Q1 I n V in Q 1 V n Figure 6.1 Modeling noise of a bipolar transistor with an equivalent resistor. NF = 4kT r b =1 1 g m eq = 4kT r b V I T C For r I b C : : r eq = b V I NF = db, relatively relatively T C eq large < 9 Ω size higher current 5

6 Low-Noise Amplifiers General Considerations FD ( NF = db) ( IIP = 10 dbm) FD : 3 P sensitivity) = P NF N 10 log B ( sin, min dbm dbm/hz db min db 174 dbm/hz F = 174 dbm NF 10 log B db FD PIIP3 F = ( F N 3 ( PIIP3 F) = Nmin 3 = ( IP3 3 min F) 1 db = 61dB ) 6

7 Low-Noise Amplifiers General Considerations Gain The minimum gain of the LNA in a heterodyne architecture is governed by 3 parameters: (driving 50 Ω) The loss of the image-reject filter (e.g. 4~5 db) The noise figure of the mixer (e.g. 10 db) IP 3 of the mixer (e.g. 5 dbm) In homodyne architectures, A LNA 0 db NF, IP Absence of the image-reject filter relaxes the gain and drive requirements of LNA Issue of flicker noise maximize the gain in the F range total 3, total 7

8 Low-Noise Amplifiers General Considerations Input and Output Impedance The interface between the antenna and the LNA: For a analog designer, he may consider the LNA as a voltage amplifier, and design its input impedance to be infinity. For a F designer, a) from noise point of view, require a transformation network to make NF b) from signal power of view, require conjugate matching 50 Ω Input matching eturn loss = 0 log Γ For simplicity, Z in = Z 0 where Γ = Z Z in in Z Z 0 0 Γ = Z 0 eturn loss: 15 to 0 db ~ 15 to 9 Ω ~ 8

9 Low-Noise Amplifiers General Considerations everse Isolation LNA A B C X LPF ADC LO Leakage cosω LO t The LO leakage occurs at Capacitive paths (including parasitics) ubstrate coupling Bond wire coupling For heterodyne receivers with a high first IF, LO leakage is relative not an issue. For homodyne topologies, LNA reverse isolation is important. 9

10 Low-Noise Amplifiers General Considerations tability Due to the presence of feedback paths (may via the parasitics) All frequencies need be considered Variations of source or load impedances tern stability factor K = where = Unconditional stable 1 If K > 1 and < 1 (for all frequencies), it is stable for any combination of source and load impedances. K 10

11 Low-Noise Amplifiers General Considerations tability K : increase the reverse isolation 1 V CC V CC Z L Z L L 1 V out C µ V b Q C 1 V out V in Q 1 V in Q 1 ( a) (b) Figure 6. tabilization by (a) neutralization (b) cascoding. 11

12 Low-Noise Amplifiers General Considerations tability Ac ground and supply loops resulting from bond wire inductance. Precaution in design, Layout, package model Low noise requirement It is often that only one transistor (usually the input device) dominant the contribution to NF. It is unlikely suitable to adopt emitter or source followers and resistive feedback. 1

13 Input Matching Common-source stage input impedance ω Z in L C F short ( 1 g ) 50 Ω m V DD L { Y } { Y } C F V out V in M 1 C L excluding I in in = = C L F C C G F ω C ω L C F F gml ( CL CF ) L ( CL CF ) ω 1 ( CL CF ) ω 1 ( C C ) ω 1 L L F g g ml >> 1, CL >> C 1 ω L C L m F L C G Figure 6.3 Common-source stage. Drawback: low voltage gain at high frequency! I { Y } in = g 50Ω { } = m L Y C ω 1 in m F C C F L g 13

14 Input Matching esistive termination topology V DD 1 NF For = 1 = P P, NF LNA 3 db V out M 1 V out V in P V in P ( a) (b) Figure 6.4 (a) esistive termination, (b) calculation of noise figure of a termination resistor. 14

15 Input Matching esistive feedback V DD Miller's effect : F L Z in F = 1 A V 1 jωc gs V out Broadband matching M 1 C L V in Drawback: F generate noise Poor reverse isolation 15

16 Negative shunt feedback Input Matching V DD V DD Z L V out M 3 noise M V out M 1 M 1 V in in (a) V in (b) tability! Figure 6.5 (a) Input resistive termination by feedback, (b) simple implementation of (a). 16

17 Input Matching Common-gate stage in 1 = g m g mb 50 Ω channel thermal I = 4kTγ n g m noise : Other noise source also degrade NF! I n M 1 M 1 M 1 V b I n V b V b V in in I NF =1 γ If γ = / 3 (long channel) I I n I (a) NF = 5 = 3. db ( b) (c) Figure 6.6 (a) Input resistive termination by feedback, (b) simple implementation of (a). Drawback: g m of M 1 cannot arbitrarily high lower bound for noise figure! 17

18 LC network tuning Input Matching Z gml1 1 in L1s CG CG s Frequency drift: need off-chip component! G D M 1 g m NF Z G g m V G C G Z in Chip area! L 1 Ground bond wire Z Figure 6.7 esistive termination by inductive degeneration. Z = Z Z g Z in G G m Z G Z = 1, Z = jωl jωc gs 18

19 Bipolar LNAs Common-emitter stage Q 1 I C be a large device relatively high Area drawback : higher input capacitance attenuating input signal C µ, C C gain I C C π base drawback : shot noise V DD C Q 1 V out Q 1 V out V in 1 (a) C 1 V in I n (b) Figure 6.8 (a) imple bipolar LNA, (b) inclusion of base shot noise. 19

20 Common-emitter stage base I shot noise : IC β n = 4kT V T Total V total noise = 4kT including r b 1 g Bipolar LNAs noise m by gm β Vtotal rb 1 NF = = 1 4kT g NF = 1 (1 g r m for min b ) β (1 g r ) m g : gm β V exp V V 1 V 1 V V 3 1 V in L 6 VT 1.7 dbm, opt = β m b m opt. noise matching power matching for I C = IIP I I 3 of the VBE0 V exp VT α 3 BE0 T IIP3 = V T additional CE in stage : in T DC linearization α 1 in T 0

21 Bipolar LNAs 900 MHz LNA (Meyer & Mack) JC 1994 V b1 Q 3 V b Q 4 V CC 1 X V out V out Q Q V in Q 1 V in Q 1 E L e B1 L e (a) gmle Zin = rb Les C 1 C s Figure 6.9 (a) Two-stage LNA, (b) biasing of the LNA. π π A 1 (b) 1

22 Bipolar LNAs L V out V out L 1 Vin Q1 Q 1 V b C 1 V in T 1 V CC Figure 6.10 Bipolar LNA incorporating transformer feedback. in Figure 6.11 Common-base LNA.

23 MO noise optimization CMO LNA 3

24 MO noise optimization CMO LNA 4

25 MO noise optimization CMO LNA 5

26 CMO LNA Linearity 6

27 Common-source LNA CMO LNA 7

28 Common-source LNA CMO LNA 8

29 900 MHz LNA in JC 1996 CMO LNA 9

30 900 MHz LNA in JC 1996 CMO LNA 30

31 1.5 GHz LNA in JC 1997 CMO LNA 31

32 1.5 GHz LNA in JC 1997 CMO LNA 3

33 CMO LNA 1.5 GHz differential LNA in JC

34 CMO LNA 1.5 GHz differential LNA in JC

35 CMO LNA 1.5 GHz differential LNA in JC 1997 Current-reuse technique VDD VDD Assume that 6 6 v v v y v and 1 ( ωc x out out m1 and 1 ( ωc m7 m7 gs7 gs is large enough : is an ac ground node. g g g C jωl d ) >> ωl in ) >> 1 ( ωc v v x g m1 d : jωl d C ) : v in 6 C C v y v x 7 M 7 v out Ld C1 v in M 1 35

36 CMO LNA 1.5 GHz differential LNA in JC 1997 VDD VDD VDD VDD VDD VDD v out 6 7 v out v out M 7 M 7 C C v y M 7 Ld C1 C C Ld C1 C C V B Ld C1 M 3 v in v x M 1 v in M 1 L s v in M 1 L s 36

37 CMO LNA 1.5 GHz differential LNA in JC 1997 V DD V DD VDD Z L Z L Z L v out v out V B M VB M 3 M 4 VB v in M 1 vin M1 M v in 37

38 CMO LNA 1.5 GHz differential LNA in JC 1997 V DD V DD VDD VDD VDD VDD 6 7 v out 6 7 v out 8 9 M 7 M 7 M 8 C C L d C 1 C C C C V B M 3 L M d L V d B 3 M 3 V B v in M 1 v in v in M 1 L s Ls Ls 38

39 1.9 GHz LNA in JC 001 Folded-cascode structure Low-voltage operation CMO LNA 39

40 1.9 GHz LNA in JC µm CMO technology Power supply = 1V Power consumption = 5mW NF min = 1.6 db NF = 1.8 db for 50 Ω matching Gain = 15 db IIP 3 = 0 dbm P 1dB = 10 dbm CMO LNA 40

41 CMO LNA 900 MHz Differential LNA in JC 001 V GP V out V out V B V GN GND 41

42 CMO LNA 900 MHz Differential LNA in JC 001 V DD V GP V out V out V B V GN GND 4

43 CMO LNA 900 MHz Differential LNA in JC µm CMO technology Power supply =.7V Power consumption = 1.6mW NF =.05 db Gain = 17.5 db IIP 3 = 6 dbm everse isolation = 40 db 43

44 5.75 GHz LNA in JC 003 CMO LNA Differential transformer feedback Differential cascode 44

45 5.75 GHz LNA in JC 003 CMO LNA Differential transformer feedback Differential cascode 0.18µm CMO technology 0.18µm CMO technology Power supply = 1.0V Power supply = 1.8V Power consumption = 16mW Power consumption = 1.6mW NF min = 0.9 db NF min = 1.8 db Gain = 14. db Gain = 14.1 db IIP 3 = 0.9 dbm IIP 3 = 4. dbm 45