Feedback Transimpedance & Current Amplifiers

Transcription

1 Feedback Transimpedance & Current Amplifiers Willy Sansen KULeuven, ESATMICAS Leuven, Belgium Willy Sansen

2 Table of contents Introduction Shuntshunt FB for Transimpedance amps. Shuntseries FB for Current amplifiers Transimpedance amplifiers for low noise and high frequencies Willy Sansen

3 Input & output impedances 1 H = Output Shunt Series Input R OUT = R OUTOL 1LG R OUT = R OUTOL (1LG) Shunt R IN = R INOL 1LG = A R i OUT = A I Series R IN = R INOL (1LG) v IN = A V i OUT v IN = A G Willy Sansen

4 Table of contents Introduction Shuntshunt FB for Transimpedance amps. Shuntseries FB for Current amplifiers Transimpedance amplifiers for low noise and high frequencies Willy Sansen

5 Shuntshunt FB configuration R IN v IN A 0 v IN A R OUT R O << R NP >> A R = = R IN 0 R OUT 0 Willy Sansen

6 Shuntshunt FB : loop gain A 0 v IN v INLG = 0 v IN R O << LG LG = LG v INLG R NP >> A vol A Willy Sansen

7 Shuntshunt FB : input resistance R IN v IN A 0 v IN A R OUT R O << R IN = v IN = R INOL 0 LG R NP >> Open Loop R INOL = R IN (A v = 0) = R NP //( R O ) Willy Sansen

8 Shuntshunt FB : output resistance = 0 v IN A 0 v IN A R OUT R O << Open Loop R OUTOL R OUT = 0 LG R NP >> R OUTOL = R OUT (A v = 0) = R O //( R NP ) R O Willy Sansen

9 Shuntshunt FB pair V DD M1 M A R = = LG = g m1 r o1 R IN = 0? LG 1/g m R OUT = 0 LG Willy Sansen

10 Shuntshunt FB pair with resistors v IN M3 M1 R 1 V DD M v IN M M3 R M1 V DD R 1 vout1 A R = = A R1 = A R = R 1 R R Ref.Cherry, Proc. IEE, Feb.63, ; Holdenried, JSSC Nov.04, Willy Sansen

11 Current detector with voltage amp. R L Q Q 3 = Q 1 R E C L = 360 Ω f T = 40 GHz r B = 0 Ω BW = 10 GHz I TOT = 10 ma Ref.Baureis, JSSC June 1993, Willy Sansen

12 Shuntshunt FB triple M1 M M3 M4 V DD LG = A v1 A v A v3 A vi = g mi r oi A R = R IN = 0 LG 1/g m4 R OUT = 0 LG Willy Sansen

13 Shuntshunt FB triple: easier biasing V DD A R = M3 LG = A v1 A v A v3 M M4 A vi = g mi r oi M1 R IN = 0 LG 1/g m4 R OUT = 0 LG Willy Sansen

14 CMOS preamplifier for optical communications Two stages possible if fully differential! 0 kω 500 Ω tracking of R1 & Rf Ref.Phang, Johns, CASII July 1999 Willy Sansen

15 Differential shuntshunt FB pair A R = LG = A v1 A v A v1 = g m1 r o1 A v = g m r o R IN = 0 LG /g m3 R OUT = 0 LG Willy Sansen

16 Current detector with voltage amplifier R IN = v IN = A 1 A C p R L A A R = LG = A 1 A = A 1 =g m R L A f 3dB = 1 π R IN C p Willy Sansen

17 Single MOST with shuntshunt FB V DD A R = (if >> 1/ g m ) LG = g m r o R R IN = F r o 0? LG r o R OUT = 0? LG Ref.Cherry, Proc. IEE, Feb.63, Willy Sansen

18 Single bipolar transistor with shuntshunt FB V DD A R = (if >> 1/ g m ) Far from ideal!! Output loading : r π r o reduces the LG!! LG = g m r o r π r o r π ( r o ) // r π R IN = 0? LG r R OUT = o // ( r π ) 0? LG Willy Sansen

19 Cascode with shuntshunt FB V DD A R = LG = g m1 r o1 g m r o r R IN = OUT 1 M 0 LG g m1 M1 r OUT = r o1 g m r o r OUT R OUT = 0 LG 1 g m1 Willy Sansen

20 MOST Shuntshunt FB triple V DD A R = M3 LG = A v1 A v A v3 M1 M A vi = g mi r oi r o3 R IN = 0 LG r o3 R OUT = 0 LG Willy Sansen

21 Bipolar Transistor Shuntshunt FB triple V DD A R = LG = A v1 A v A v3 Q1 Q Q3 A v1 = g m1 (r o1 //r π ) A v = g m (r o //r π3 ) A v3 = g m3 R OUTOL R OUTOL = r o3 //( r π1 ) R OUT = R OUTOL 0 LG Output loading : r π3 r o3 reduces the LG!! (R R IN = F r o3 ) //r π1 0 LG Willy Sansen

22 Shuntshunt FB with nonideal current source R IN = R G R IN RG A 0 RS A 0 A R = A R = if R S > A0 LG = A 0 LG = A 0 R IN = A 0 R G = A0 R IN = R G // R S Willy Sansen

23 Shuntshunt FB with voltage source R IN RG R IN R G RS A 0 R v S OUT v IN A0 A R = if R S > A0 A R = if R S > A0 LG = A 0 LG = A 0 R G = A0 R IN = R G //R S R G = A0 R IN = R G R S Willy Sansen

24 Shuntshunt feedback : Gain and ROUT R v IN R 1 LG = A A R A A R = R if R 1 > 0 A0 v IN = v IN 1 A v = A R R 1 ROUT = R OUTOL LG R A v = R1 Willy Sansen

25 Shuntshunt FB pair with with voltage source R G V DD A R = A v = R S v IN R S M1 M LG = g m1 r o1 R IN = R S R G R G = = 0 LG g m1 r o1 if R S > A0 1/g m R OUT = 0 LG Willy Sansen

26 Shuntshunt FB pair with input loading V DD A R = Q1 Input loading : r π1 Q LG = g m1 r o1 R R IN = F // r π1 0 LG R OUTOL R OUT = 0 LG 1 R OUTOL = g m r π1 r π1 r o1 β = gm1 r o1 Willy Sansen

27 Shuntshunt FB pair with voltage source R B R L V DD A R = A v = R S v IN R S Q1 Q R E LG = g m1 R L r π1 r π1 //r π1 R B = 0 LG R IN = R S R B Input loading : r π1 R OUTOL R OUT = 0 LG 1 R OUTOL = g m R L β Willy Sansen

28 Nonideal singletransistor shuntshunt FB R B R S R L V DD A R LG g m r olf R IN = R S R B A v R S v IN r π //( r ol ) R B 0 LG r olf R OUT 0?? LG Output loading : r ol r ol = r o //R L r olf = r o //R L // Input loading : r π Willy Sansen

29 Nonideal singletransistor Feedback R L V DD A R = LG =? A v = R S R S R IN =? v IN R E R OUT =? Output loading : r ol r ol = r o //R L Input loading : r π Willy Sansen

30 Shuntshunt feedback in Rightleg drive i B i B d R A A 0 vb R P v B R B A 0 R P i B 10 µa RMS for 0 V RMS (50 Hz) through 150 pf v B i B = R P R B A 0 1 Willy Sansen

31 Table of contents Introduction Shuntshunt FB for Transimpedance amps. Shuntseries FB for current amplifiers Transimpedance amplifiers for low noise and high frequencies Willy Sansen

32 Shuntseries feedback : Gain, RIN & ROUT V DD LG = A 0 R IN A 0 R i OUT R OUT R //R E i OUT R E A I = 1 R R E R IN = R * LG 0 R OUTOL = r o (1 g m R E ) R OUT =R OUTOL LG R E > 1/g m R > 1/g m R * = R R E /(1g m R E ) R Willy Sansen

33 Shuntseries feedback with load RL R IN A 0 R E > 1/g m R R L R > 1/g m R E R OUTT V DD R OUT LG = A 0 A I = 1 R R E AR =A I R L R R IN = 0 LG R OUT =R OUTT //R L R L R OUTT =R OUTTOL LG R OUTTOL = r o (1 g m R E ) Willy Sansen

34 Ideal current buffer i OUT A I = 1 R IN A 0 R OUT 0 R E LG = A 0 1/g m R IN = 0 LG R OUTOL = r o (1 g m R E ) R E > 1/g m R OUT =R OUTOL LG Willy Sansen

35 Ideal current mirror R IN M1 V ref 0. V A 0 1 : B i OUT = B A I = B R OUT M R INOL LG = g m1 r o1 A 0 R IN = = 0 LG R INOL = r o1 1 g m1 A 0 R OUT = r o Willy Sansen

36 Gain boosting V B A gb I B v out LG = A gb v in M M1 C L 1/g m R E = 0 LG R OUTOL = r o (1 g m r o1 ) A v = A gb (g m r DS ) 1 (g m r DS ) R OUT =R OUTOL LG Hosticka, JSSC Dec.79, pp ; Sackinger, JSSC Febr.90, pp. 8998; Bult JSSC Dec.90, pp Willy Sansen

37 Differential current amplifier Ref. Umminger, JSSC Dec.95, Willy Sansen

38 Linear laser diode driver i D v IN R 1 A 0 g m i OUT Opt. fiber i OUT = k = k v IN R 1 i D = i OUT k LG = g m A 0 k Willy Sansen

39 Table of contents Introduction Shuntshunt FB for Transimpedance amps. Shuntseries FB for Current amplifiers Transimpedance amplifiers for low noise and high frequencies Willy Sansen

40 Optical receiver : Current or voltage amplifier I IN I IN A v A R = I IN = A R I IN Willy Sansen

41 Current detector with voltage amplifier v IN = A 1 A 1 C 1 R P F A s 1 A C P =C D C GS R L A 1 =g m R L A=A 1 A A T = = 1 C 1 R P F A s 1 A A 1 A 1 RF C P s Noise matching : C D = C GS A R BW (THzΩ) = A 1 A π C P Willy Sansen

42 Current detector with voltage amplifier v IN R = F 1 R L C L s A 1 as bs 1 A R L C L A=A 1 A A a = C P A 1 A b = C P R L C L A 1 A C P =C D C GS A 1 =g m R L No peaking if R L < 4g m A C P C L 1 = 1 as bs Willy Sansen

43 BW in voltage/current amplifier R L M M1 M M1 R E R E R S R S >> 1/g m1 BW = A v1 π (C GS1 C D ) BW = 1 π (C GD C DB1 ) Willy Sansen

44 Current detector with input cascode BW = A v R L1 R L π //R L1 C T M1 M M3 CT = CGS Av CGD A v = g m R L R S R E C L = Z IN independent of f! R S >> 1/g m1 R OUT = 1/g m3 Av Vanisri, etal, JSSC June 95, pp Willy Sansen

45 Current detector with regulated cascode 5 V 17 ma C D = 0.5 pf = 800 Ω BW = 1 GHz g mb = 3 g m1 BW independent of C D! Current noise : R S & // R 1 Park, JSSC Jan. 04, 1110 Willy Sansen

46 Noise sources of detector voltage amplifier di R di D dv A i i R L C L di D = qi D df 4kT di R = df dv A = 4kT ( /3 ) df g m Willy Sansen

47 Noise density of detector voltage amplifier di ieq i i R L CL dv A di ieq = di D di R di D di R if > /3 g m Willy Sansen

48 Noise sources of detector current amplifier di D di A i i C L di D = q I D df di A = 4kT g m df 3 Willy Sansen

49 Noise density of detector current amplifier di ieq di A i i C L di ieq = di D 4kT g m df is transistor noise! 3 Willy Sansen

50 Comparison of noise densities Voltage amp.: i IN = di 4kT R = df Current amp.: i IN = di A = 4kT g m df 3 Voltage amplifier better when > 3 1 g m Willy Sansen

51 Comparison of integrated noise Large I D : i IN = di π D (BW ) Small I D : Voltage amp.: i IN = di π R (BW ) = kt R L R ( L ) g m C P Current amp.: i IN = di π A (BW ) = 3 kt g m C L Voltage amplifier better when > 3 4 R L Willy Sansen

52 CMOS photodiode amplifier M M1 M3 150 kω x 10 MHz = 18 THzΩ 0.5 pa/ Hz 450 MHz per cell Ref.Ingels, JSSC Dec 1994, Willy Sansen

53 CMOS wideband amplifier cell M I DS M 1 & M 3 : same V GS & V DS K n K p All L are L min M1 M3 A v = g m1 g m g m3 g m = K n I DS W/L I DS1 = λ I DS I DS3 = (1 λ) I DS V GS1 = V GS3 : W 3 = W 1 1 λ λ Willy Sansen

54 CMOS wideband amplifier : gain and bandwidth 10 8 A v λ 1 λ W ( 1 ) λw BW λ BW = g m3 π C n (1 λ) λw ~ 1 W 1 ( λ) λw W 1 = W = 4 C n = C DB1 C GS3 C DB3 C DB C DB C GS kw k ff/µm Willy Sansen

55 Integrated resistor M? Poly R : large size : large L distributed C : 45 o phase shift at 100 MHz M1 M3 f 3dB = 1 π.43 R S C 0 L R S = sheet res. (Ω / ) C 0 = unit cap. (F/cm ) MOST : W = 1.3 µm & L = 1 µm allows dynamic compression Glaser; IC Engineering Add.Wesley, p.13 Willy Sansen

56 Gain compression F Willy Sansen

57 1 Gb/s 1 kω transimpedance stage pmost vs nmost : nmost R increases for larger diode currents! pmost gives compression! C d = 0.8 pf C GS Capacitive noise matching! BW = 500 MHz 5 ma (5V) 0.7 µm CMOS Ref.Ingels, JSSC July 1999, Willy Sansen

58 Highfrequency Resistance RF R 4 R = = R 3 R 1 R 1 R = 00 kω R 3 R 4 = 4 kω 0.5 pf sees 1/g m1 Poly = 00 kω would cut off around 67 MHz! C d = 0.1 pf 180 kω 380 MHz 68 THzΩ 14 ma (5 V) 0.6 µm BiCMOS Seidl, ISSCC 04, Willy Sansen

59 BICMOS transimpedance amplifier 178 MHz 8 kω 178 MHz 1 pa/ Hz Ref.Meyer, JSSC June 1994, Willy Sansen

60 BICMOS transimpedance amplifier R A v = 1 //.. 5 kω = = /g m R i = = 40 Ω 1 A v C i = (1 A v ) C = 4 pf di 4kT i = qi B1 df df 1 = ( ) A /Hz 8 kω 178 MHz 1 pa RMS / Hz 178 MHz Ref.Meyer, JSSC June 1994, Willy Sansen

61 Lowvoltage transimpedance amplifier I B1 I B I B1 I B M1 M1 M1 M1 If > 1/g m1 : = Ref.Phang, Johns, ISSCC 001, 1819 Willy Sansen

62 75 Mb/s optical receiver in CMOS C d = 1 pf (40 µa).4 kω 45 MHz 75 Mb/s 11 pa RMS / Hz 0.35 µm CMOS 1 V (1 ma) Ref. Phang, ISSCC Willy Sansen

63 GaAs 10 Gb/s receiver HP GaAs MODIC : depletion nmost s 560 V/W flipchip PD : 3 db at 7. GHz 10 pa/ Hz wire bond : 3 db at 4. GHz 0 pa/ Hz Willy Sansen

64 Table of contents Introduction Shuntshunt FB for Transimpedance amps. Shuntseries FB for Current amplifiers Transimpedance amplifiers for low noise and high frequencies Willy Sansen