A 10 d bm 25 dbm, 0.363 mm2 two stage 130 nm rf cmos power amplifier

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This paper proposes a 2.4 GHz RF CMOS Power amplifi
er and variation in its main performance
parameters i.e, output power, S-parameters and powe
r added efficiency with respect to change in supply
voltage and size of the power stage transistor. The
supply voltage was varied form 1 V to 5 V and the
range
of output power at 1dB compression point was found
to be from 10.684 dBm to 25.08 dBm respectively.
The range of PAE is 16.65 % to 48.46 %. The width o
f the power stage transistor was varied from 150 μm
to 500 μm to achieve output power of range 15.47 dB
m to 20.338 dBm. The range of PAE obtained here is
29.085 % to 45.439 %. The total dimension of the la
yout comes out to be 0.714 * 0.508 mm
2
.

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A 10 d bm 25 dbm, 0.363 mm2 two stage 130 nm rf cmos power amplifier

  1. 1. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 A 10 dBm-25 dBm, 0.363 mm2 TWO STAGE 130 nm RF CMOS POWER AMPLIFIER Shridhar R. Sahu1 and Dr. A. Y. Deshmukh2 1 Research Scholar, Department of Electronics Engineering, G. H. Raisoni College of Engineering, Nagpur, India 2 Professor, Department of Electronics Engineering, G. H. Raisoni College of Engineering, Nagpur, India Abstract This paper proposes a 2.4 GHz RF CMOS Power amplifier and variation in its main performance parameters i.e, output power, S-parameters and power added efficiency with respect to change in supply voltage and size of the power stage transistor. The supply voltage was varied form 1 V to 5 V and the range of output power at 1dB compression point was found to be from 10.684 dBm to 25.08 dBm respectively. The range of PAE is 16.65 % to 48.46 %. The width of the power stage transistor was varied from 150 µm to 500 µm to achieve output power of range 15.47 dBm to 20.338 dBm. The range of PAE obtained here is 29.085 % to 45.439 %. The total dimension of the layout comes out to be 0.714 * 0.508 mm2. Keywords RF CMOS, PAE, Output Power, S-parameters, Matching Networks 1. INTRODUCTION CMOS RFICs are Radio Frequency Integrated circuits in CMOS technology operated in radio frequency range. RF Power Amplifiers are part of the transmitter front-end used to amplify the input power to be transmitted [1][3]. The main performance parameters for the power amplifier are the level of output power it can achieve, depending on the targeted application, linearity, and efficiency. The two basic definitions for the efficiency of the power amplifier are drain efficiency (DE) which is the ratio between the RF output power to the dc power dissipated, and the power added efficiency (PAE) which is the ratio between the difference of the RF output power and the RF input power to the total dc power of the circuit. The PAE is a more practical measure as it is responsible for the power gain of the amplifier [1]. DOI : 10.5121/vlsic.2013.4509 107
  2. 2. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 DE = P out ( RF ) P dc (2) RFICs are fabricated using CMOS, GaAs Hetero-Junction Bipolar Transistor (HBT), SiGe BiCMOS, , GaN High Electron Mobility Transistor (HEMT) technologies. Existing power amplifiers mostly use GaAs (Gallium Arsenide) or GaN (Gallium Nitride) for high output power. But it also leads to high power dissipation, large chip area and more cost. The GaAs technology provides high output power at high frequency, but it is quite expensive and the uniformity of the device structure may be affected due to process variations [6]. The GaN process also operates at higher frequencies and deals with high power capacity but due to wide band gap materials used more voltage supply is needed for operation which in turn leads to high power dissipation [7]. CMOS power amplifiers can also be operated at high frequencies and by using some techniques output power can be increased. CMOS power amplifiers show more linearity as compared to GaAs and GaN technologies. As CMOS can operate on low power supplies there is drastic decrease in overall power dissipation of the circuit and hence better PAE can be expected. CMOS power amplifiers are cost effective and use minimum chip area for fabrication. The main objective behind this paper is to design a CMOS Power Amplifier for 2.4 GHz WLAN application and observe change in its important parameters such as s-parameters, output power, power added efficiency with change in supply voltage and size of the power stage transistor. The tool used for designing this circuit is ADS (Advanced Design System) tool of Agilent Systems. This circuit is designed in RFCMOS 130 nm technology. The layout of this paper is follows: Initially this paper deals with the schematic of the CMOS power amplifier, then the simulation results obtained by varying supply voltage and size of second stage transistor. Layout of the designed circuit is drawn in Tanner Tool. Finally, conclusions are drawn out after observing the simulation results. 2. SCHEMATIC A schematic of the CMOS power amplifier is shown in the figure 1. Driver stage and Power stage with the supply and bias network are main parts of the power amplifier. A cascode topology is used in the driver stage and a basic power amplifier topology is used in the power stage. The circuit is operated in 2.4 GHz ISM band. vdd L L3 R R2 T SMC_CM013RF_PMOS vdd M4 V _DC V1 V dc=2.5 V L L4 L L6 C C6 C C3 C C4 L L5 C C2 T SMC_CM013RF_NMOS_RF M2 R R3 V load I_Probe I_Probe1 T erm T erm1 T SMC_CM013RF_NMOS_RF M3 vdd R R1 T SMC_CM013RF_PMOS M6 T SMC_CM013RF_NMOS M7 T S MC_CM013RF_NMOS M5 C C1 C C5 L L1 P_1T one PORT 1 Freq=2.4 GHz T SMC_CM013RF_NMOS_RF M1 L L2 Fig. 1. Schematic of complete Two Stage CMOS Power Amplifier 108
  3. 3. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 A cascode topology is implemented in the first stage. The transistor M1 is the main amplifying device of this stage and transistor M2 is cascaded with M1. An inductor of a large value is connected between the drain of M2 and VDD which opposes the change in current and the cascaded transistor is to prevent large flow of drain current through M1. The transistor M2 is biased in saturation. Transistor M1 is biased by a MOSFET only bias circuit whose output is 0.5 Volts to operate in triode region. The transistor was first analyzed with different biasing voltages and found to be operating better at 0.5 V in similar conditions. An input matching network is connected to the driver stage i.e., the input stage for input impedance matching. For this matching purpose gate inductance Lg (L1) and source inductance Ls (L2) are used. The values of these inductances and the size of the transistors are such selected that the operation of the circuit is tuned to the resonance frequency of 2.4 GHz. The gate length of the transistors is fixed at 130nm and the width of gate is varied. The output power of this topology is not as high as the power stage but the isolation provided between output and input is very high. Also the dc power consumed by this circuit is far less than the power stage circuit. The dc current through this stage is 6.31 mA at 2.5 V. The second stage is mainly responsible for power amplification considering the overall circuit. The size of the transistor used in this stage is large as compared to the size the transistors used in the driver stage. A big fat inductance is connected between the dc supply and the drain of the transistor M3. The output of the driver stage is fed to the gate of the transistor M3 through the capacitor C6. The dc current here is controlled by varying the size of the transistor. The amplification of the signal also depends on the bias voltage supply. Bias voltage is 0.75 V. Output matching network is connected at the output side for output impedance matching. Here, a LC tank circuit is designed for matching purpose and to tune the circuit to its operating frequency, so that the output return loss is better at resonance frequency. The total dc current of this stage comes out to be 83.5 mA at 2.5 V. 3. SIMULATION RESULTS S – Parameters are an important part of Power amplifiers. There are four s-parameters essential to observe after designing a power amplifier. They are input return loss S(1,1), output return loss S(2,2), gain S(2,1) and isolation loss S(1,2). Power calculations are carried out at 1dB compression point of the gain of the circuit. As shown in the figure 3, graph of gain in dB is plotted v/s input power in dBm. According to the figure 1dB compression point is obtained at -22.7 dBm of input power. Output power is observed at the same input power which comes out to be 20.028 dBm. This output power is known as output power at 1dB compression point. The maximum output power delivered by this circuit is 22.002 dBm. The unit used for power calculations of a power amplifier is dBm instead of watts. The conversion of watts to dBm and dBm to watts is given as in equation (3). The equation for power gain is given as in equation (5). Power added efficiency; the factor by which the power amplifiers are analyzed is the deciding parameter between different types of power amplifiers. This CMOS power amplifier operating at 2.4 GHz with a main supply of 2.5 V gives PAE of 44.669 % at 1dB compression point. The maximum PAE achieved by the circuit is 70.196 %. These values can be observed in figure 8 where on left y axis pout is plotted and on right y axis PAE is plotted. The equations for the same are given in equation 6, 7 and 8. 109
  4. 4. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 P(W ) ) 1mW P(dBm) = 10 × log( ( P (W ) = 10 P ( dBm ) −3 ) 10 (4) P P P ( dB ) = 10 × log( PAE PAE = P out (1dB ) P out (W ) (W ) in ) (5) (W ) − P in (1dB ) (W ) P out (max) dc (W ) (6) (W ) − Pin (W ) P dc (W ) (7) = V dd × I dc (8) m1 freq= 2.400GHz dB(S(1,1))=-11.132 m2 freq= 2.400GHz dB(S(2,2))=-12.467 m4 m3 50 -60 40 -80 m3 freq= 2.400GHz dB(S(2,1))=43.745 30 10 -120 m1 m2 -10 -140 dB (1 )) (S ,2 -100 20 0 m4 freq= 2.400GHz dB(S(1,2))=-61.889 -160 -20 0.0 0.5 1.0 1. 5 2. 0 2.5 3.0 3.5 4.0 4.5 5.0 f req, GHz Fig. 2. S - Parameters m5 45 m6 m5 pin= -45.800 gain=43.752 40 35 G in( B a d) dc max = d (S ,1)) B (1 d (S ,1)) B (2 d (S ,2)) B (2 P 1dB (3) 30 m6 pin= -22.700 gain=42.728 25 20 15 10 -50 -40 -30 -20 -10 0 10 Pin (dBm) Fig. 3. Obtaining 1dB compression point 110
  5. 5. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 m8 pin= -3.900 pout=22.002 Max m8 m7 pin= -22.700 pout=20.028 25 m7 100 20 m9 pin= -22.700 PAE=44.669 80 m10 60 10 m9 m10 pin= -3.900 PAE=70.196 Max 5 0 40 PAE (% ) Pout (dBm) 15 20 -5 0 -10 -50 -40 -30 -20 -10 0 10 Pin (dBm) Fig. 4. Output Power and Power Added Effciency 3.1 Variation in Output Power, S-Parameters and PAE with change in Supply Voltage The supply voltage was varied from 1 V to 5 V. The operating frequency was kept constant i.e, 2.4 GHz. The values of s-parameters, output power, PAE achieved are tabulated in table 1. The range of output power at 1dB compression point observed is 10.684 dBm to 25.08 dBm. The range of maximum output power is 14.286 dBm to 27.217 dBm. Power added efficiency at 1dB compression point is calculated to be 16.65 % at 1 V to 48.46 % at 3.3 V. Maximum PAE is 38.12 % at 1 V to 77.407 % at 3.3 V. The overall DC current observed here is 70.23 mA at 1 V to 168 mA at 5 V. These results can also be observed in figures 5, 6, & 7. 3.2 Variation in Output Power, S- parameters and PAE with change in Size of Power stage Transistor Initially the width of the second stage transistor was 300 µm, i.e, 30 gate fingers with 10 µm width of single gate finger. The number of gate fingers was varied to change the size of the transistor. The gate fingers were varied from 15 to 50 numbers making the width effectively 150 µm to 500 µm. The results obtained are tabulated in table 2. The operating voltage and operating frequency were kept constant at 2.5 V and 2.4 GHz respectively. The number of gate fingers here is denoted as F. The range of output power at 1dB compression point observed is 15.47 dBm to 20.338 dBm. The range of maximum output power is 20.702 dBm to 22.354 dBm. Power added efficiency at 1dB compression point is calculated to be 29.085 % at 150 µm gate width to 45.439 % at 25 um gate width. The overall DC current observed here is 48.4 mA at 15 gate fingers to 143.7 mA at 50 gate fingers. These results can also be observed in figures 8, 9, & 10. 111
  6. 6. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 m16 pin= -14.800 pout=14.286 Vdd=1.000000 Max m7 pin= -29.800 pout=10.684 Vdd=1.000000 30 Pout (dBm) 20 m15 pin= -3.500 pout=22.098 Vdd=2.500000 Max m18 m14 pin= -2.100 pout=27.217 Vdd=5.000000 Max m14 Vdd=5.000 Vdd=3.300 Vdd=3.000 Vdd=2.500 Vdd=1.800 m15 m17 m16 Vdd=1.200 Vdd=1.000 m7 10 m17 pin= -22.700 pout=20.021 Vdd=2.500000 0 m18 pin= -18.700 pout=25.080 Vdd=5.000000 -10 -50 -40 -30 -20 -10 0 Pin (dBm) Fig. 5. Output Power at different supply voltages m26 indep(m26)= -44.400 plot_vs(Idc, pin)=-70.291 Vdd=1.000000 m26 0 Idc (mA) -50 m24 indep(m24)= -16.000 plot_vs(Idc, pin)=-90.048 Vdd=2.500000 Vdd=1.000 Vdd=1.200 Vdd=1.800 Vdd=2.500 Vdd=3.000 Vdd=3.300 m24 -100 m25 indep(m25)= -12.400 plot_vs(Idc, pin)=-167.923 Vdd=5.000000 -150 m25 Vdd=5.000 -200 -50 -40 -30 -20 -10 0 Pin (dBm) Fig. 6. Total DC Current at different Supply voltages 100 PAE (% ) 80 60 40 m20 pin= -14.800 PAE=38.120 Vdd=1.000000 Max m21 pin= -29.800 PAE=16.651 Vdd=1.000000 m22 pin= -3.500 PAE=71.818 Vdd=2.500000 Max m22 m19 m23 pin= -22.700 PAE=44.635 Vdd=2.500000 m23 m9 m20 Vdd=3.300 Vdd=3.000 Vdd=2.500 Vdd=5.000 Vdd=1.800 Vdd=1.200 Vdd=1.000 m9 pin= -18.700 PAE=38.361 Vdd=5.000000 m21 20 m19 pin= -2.200 PAE=62.680 Vdd=5.000000 Max 0 -50 -40 -30 -20 -10 0 Pin (dBm) Fig. 7. Power Added Efficiency at different supply voltages 112
  7. 7. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 Table 1. Variation in Output Power, S- Parameters and PAE with change in Supply voltage OperatingS – Parameters (dB) Voltage (V) Vdd S(1,1) S(2,2) 1.0 -10.928 -12.048 1.2 -11.569 -12.804 1.8 -12.477 -13.467 2.5 -11.132 -12.467 3 -10.034 -11.368 3.3 -9.579 -10.738 5 -6.285 -8.32 S(2,1) 41.474 42.227 43.403 43.745 43.813 43.891 44.769 Total Dc Current (mA) IDC 70.3 72.6 79.5 90.05 100 108 168 S(1,2) -60.822 -60.992 -61.367 -61.889 -62.39 -62.755 -65.214 Output Power (dBm) Power Added Efficiency (%) Pout1dB 10.684 12.612 16.724 20.021 21.6 22.365 25.08 PAE1dB PAEmax 16.65 38.12 20.952 44.213 31.958 63.854 44.635 71.818 48.01 76.279 48.466 77.407 38.361 62.68 Poutmax 14.286 15.86 19.327 22.098 23.623 24.411 27.217 Operating Frequency: 2.4 GHz P u (d m ot B ) m12 pin=-5.000 pout=20.706 Fingers=15.000000 Max 25 m11 pin=-27.500 pout=15.470 20 Fingers=15.000000 m24 pin=-3.900 pout=22.002 Fingers=30.000000 Max m25 m23 m22 pin= -8.100 pout=22.354 Fingers=50.000000 Max m22 m24 Fingers=50.000 Fingers=45.000 m12 Fingers=40.000 Fingers=35.000 Fingers=30.000 Fingers=25.000 Fingers=20.000 Fingers=15.000 m11 m25 pin=-22.700 pout=20.028 Fingers=30.000000 m23 pin= -20.700 pout=20.018 Fingers=50.000000 15 10 5 0 -50 -40 -30 -20 -10 0 Pin (dBm) Fig. 8. Output Power with change in size of power stage transistor m19 indep(m19)= -38.100 plot_vs(Idc, pin)=-48.456 Fingers=15.000000 m20 indep(m20)= -3.000 plot_vs(Idc, pin)=-90.129 Fingers=30.000000 m19 -40 Fingers=15.000 -60 Fingers=20.000 Idc (m ) A -80 Fingers=25.000 m20 Fingers=30.000 -100 -120 -140 Fingers=35.000 m21 indep(m21)= -7.700 plot_vs(Idc, pin)=-143.767 Fingers=50.000000 Fingers=40.000 Fingers=45.000 m21 Fingers=50.000 -160 -50 -40 -30 -20 -10 0 10 Pin (dbm) Fig. 9. Total DC Current with change in size of power stage transistor 113
  8. 8. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 m18 pin= -5.000 PAE=96.851 Fingers=15.000000 Max 100 P E(% A ) 80 60 40 20 m14 pin= -3.900 PAE=70.196 Fingers=30.000000 Max m13 pin= -8.200 PAE=47.803 Fingers=50.000000 Max m18 m17 pin= -27.500 PAE=29.085 Fingers=15.000000 Fingers=15.000 Fingers=20.000 m14 Fingers=25.000 Fingers=30.000 Fingers=35.000 Fingers=40.000 Fingers=45.000 Fingers=50.000 m15 m13 pin= -22.700 m15 PAE=44.669 Fingers=30.000000 m17 m16 m16 pin= -20.700 PAE=27.938 Fingers=50.000000 0 -50 -40 -30 -20 -10 0 Pin (dBm) Fig. 10. Power Added Efficiency with change Size of Power stage transistor Table 2. Variation in Output Power, S- Parameters and PAE with change in size of power stage transistor Size of Power S – Parameters (dB) Stage Transistor (W/L) µm (10*F)/0.13 S(1,1) S(2,2) 15 -6.578 -9.295 20 -8.179 -15.293 25 -9.614 -16.637 30 -11.132 -12.467 35 -11.952 -9.504 40 -12.886 -7.772 45 -13.631 -6.493 50 -14.299 -5.638 S(2,1) 43.857 44.176 43.975 43.745 43.114 42.673 42.082 41.605 S(1,2) -61.92 -61.557 -61.496 -61.889 -62.432 -62.860 -63.344 -63.767 Total DC Output Power Current (dBm) (mA) IDC Pout1dB Poutmax 48.4 15.47 20.702 62.4 17.995 21.381 76.3 19.378 21.761 90.1 20.028 22.002 104 20.317 22.139 117 20.338 22.239 131 20.263 22.291 143.7 20.018 22.354 Power Added Efficiency (%) PAE1dB 29.085 40.408 45.439 44.669 41.477 36.889 32.542 27.938 PAEmax 96.851 87.913 78.449 70.196 62.93 56.982 51.863 47.803 Operating Voltage: 2.5 V Operating Frequency: 2.4 GHz 4. LAYOUT The layout of the designed power amplifier drawn in Tanner tool is shown in figure 11.This layout occupies total die area of 0.363 mm2. This layout is designed to be operating at 2.5 dc supply and the width of power stage transistor is 300 µm. The total dc current flowing through this circuit is 90.1 mA. Metal 4 is used for VDD and ground lines and as its current flowing density is 1.6 mA per 1 µm, 120 µm metal 4 width is used. 114
  9. 9. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 Fig. 11. Layout of RF CMOS Power Amplifier 5. CONCLUSIONS CMOS power amplifiers provide high output power with high efficiency. The values of VDD supply and size of power transistor were varied to observe the changes in output power, sparameters and power added efficiency. As shown in the results wide range of output power was achieved with relatively high efficiency. From the results it can be concluded that this power amplifier shows best performance with VDD 2.5 V and width of power stage transistor to be 300 µm. This wide range of output power helps this circuit in application of Bluetooth to WLAN. REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] M.Hella, M.Ismail.: RF CMOS Power Amplifiers: Theory, Design and Implementation. Ohio State University Thomas H. Lee.: The Design of CMOS Radio Frequency Integrated Circuits. Second Edition, Cambridge University Press Ho Ka Wai.: 1-V CMOS Power Amplifier for Bluetooth Applications, Hong Kong University of Science and Technology, 2002 Kyu Hwan An.: CMOS RF POWER AMPLIFIERS FOR MOBILE WIRELESS COMMUNICATIONS. Georgia Institute of Technology, 2009 Ravinder Kumar, Munish Kumar, Balraj.: Design and Implementation of a High Efficiency CMOS Power Amplifier for Wireless Communication at 2.45 GHz. 2012 International Conference on Communication Systems and Network Technologies. Wenyuan Li, Yulong Tan.: 2.4GHz Power Amplifier with Adaptive Bias Circuit. Institute of RF- & OE-ICs Southeast University Nanjing, China, 2012 International Conference on Systems and Informatics (ICSAI 2012) G. Monprasert, P. Suebsombut, T. Pongthavornkamol, S. Chalermwisutkul.: 2.45 GHz GaN HEMT Class-AB RF Power Amplifier Design for Wireless Communication Systems. The Sirindhorn International Thai-German Graduate School of Engineering (TGGS), King Mongkut’s University of Technology North Bangkok, IEEE 2010 Yongbing Qian, Wenyuan Li, Zhigong Wang.: 2.4-GHz 0.18-µm CMOS Highly Linear Power Amplifier. Institute of RF- & OE-ICs, Southeast University, 210096 Nanjing, China, The 2010 International Conference on Advanced Technologies for Communications, 2010 IEEE 115
  10. 10. International Journal of VLSI design & Communication Systems (VLSICS) Vol.4, No.5, October 2013 [9] Cheng-Chi Yen Student Member, IEE and , Huey-Ru Chuang IEEE.: A 0.25um 20-dBm 2.4-GHz CMOS Power Amplifier With an Integrated Diode Linearizer. MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 13, NO. 2, FEBRUARY 2003 [10] Chia-Jun Chang, Po-Chih Wang, Chih-Yu Tsai, Chin-Lung Li, Chiao-Ling Chang, Han-Jung Shih, Meng-Hsun Tsai, Wen-Shan Wang, Ka-Un Chan, and Ying-Hsi Lin.: A CMOS Transceiver with internal PA and Digital Pre-distortion For WLAN 802.11a/b/g/n Applications., 2010 IEEE Radio Frequency Integrated Circuits Symposium [11] Yi Zhao, John R. Long, and Marco Spirito.: A 60GHz-band 20dBm Power Amplifier with 20% Peak PAE. 2011 IEEE [12] Ville Saari, Pasi Juurakko, Jussi Ryynanen and Kari Halonen.: lntegrated 2.4 GHz Class-E CMOS Power Amplifier. 2005 lEEE Radio Frequency Integrated Circuits Symposium. 116

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