* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download U04504127132
Integrating ADC wikipedia , lookup
Index of electronics articles wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
Nanofluidic circuitry wikipedia , lookup
Phase-locked loop wikipedia , lookup
Radio transmitter design wikipedia , lookup
Regenerative circuit wikipedia , lookup
Thermal runaway wikipedia , lookup
Power MOSFET wikipedia , lookup
Analog-to-digital converter wikipedia , lookup
Galvanometer wikipedia , lookup
Surge protector wikipedia , lookup
Oscilloscope history wikipedia , lookup
Valve audio amplifier technical specification wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Schmitt trigger wikipedia , lookup
Transistor–transistor logic wikipedia , lookup
Power electronics wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Two-port network wikipedia , lookup
Current source wikipedia , lookup
Negative-feedback amplifier wikipedia , lookup
Wilson current mirror wikipedia , lookup
Operational amplifier wikipedia , lookup
Current mirror wikipedia , lookup
Jigyasa Singh et al Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.127-132 www.ijera.com RESEARCH ARTICLE OPEN ACCESS A High Speed CMOS Current Comparator at Low Input Current Jigyasa Singh, Sampath Kumar V. JSS Academy of Technical Education, Noida – 201301, India Abstract Analysis of high speed CMOS current comparator is presented with low input impedance using a simple biasing method. The simulation results from PSPICE demonstrate the propagation delay at low input currents at supply voltages of 1.8v, 2v, 2. 2v and stability analysis using 0.25um CMOS technology. So it is suitable to high speed applications. Keywords—Current comparators, propagation delay, positive feedback, signal processing. I. INTRODUCTION Current comparators are important building blocks within many analogue circuits designs. In particular, they are used for front-end signal processing applications and increasingly within neuromorphic electronic systems [1,2]. A/D converters may be designed using current-mode technologies. Since many digital and analog circuits have been tried to switch from voltage mode to current, mode operations. Current comparators may be the key elements. It consumes less power dissipation, achieves more dynamic range and high operation speed. Thus the current mode circuit design methodology receives increasingly wide attention in recent years [3,4]. In order to detect low current with high speed, many current comparators have been proposed. The simplest current comparator with positive feedback and low input impedance is shown in fig.1 [5] i.e. Traff current comparator. When the input current (Iin) flows into the circuit through V1, Vout is high. When input current (Iin) flows out of the circuit, Vout is low. CMOS inverters at the output stage to give rail-to-rail voltage swing. If the input current is small enough, there exists a deadband problem where the input impedance is quite high during input transition thus limiting the speed of operation. www.ijera.com M1 M3 M5 V1 1 Iin Vout 2 V2 M4 M6 M2 Fig.1 For reducing the deadband region of current comparator change its biasing scheme from class B to class AB. Another approach using resistor feedback to detect small currents shown in fig.2 [6].A simple current-source inverting amplifier seems attractive for many applications, but its large output resistance prevents its use at high speed, especially for capacitive loads. High speed current comparator requires low input impedance for increased current sourcing and sinking capability. Input and output resistance can be reduced by resistive feedback in first inverting amplifier in the input stage of current comparator. More inverters are required at the output stage to produce rail-to-rail output swing. This comparator is good for high speed at low input current but the power consumption is much higher due to constant current. 127 | P a g e Jigyasa Singh et al Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.127-132 www.ijera.com Fig.2 II. 13TCURRENT COMPARATOR Since the response of original current comparators degrades drastically at low input current. One of the most significant problem of deadband has been minimized. Fig.3 shows the 13T current comparator which has one diode-connected enhance the speed. M8-M11 are the pairs of CMOS inverters to amplify the output signal. The two transistors Mp and Mn are used to adjust the inverter threshold voltage of M8 and M9 using different voltages values of Vn and Vp. For typical case Gate of Mp i.e. Vp is connected to ground and Mn i.e. Vn is connected to Vdd. Fig.3 transistor NMOS transistor instead of using two to III. PERFORMANCE ANALYSIS provide voltage drop between the gates of M1 and M2. M3 and M5 forms the reference current The 13T current comparator is simulated for various generating stage. Input current (Iin) is connected to input currents and compared with circuits of fig.[1] the first stage of the circuit. The drain and source of and fig.[2] at Vdd=1.8v,2v,2.2v using 0.25um. M4 is connected to the gates of M6 and M7. Fig.4,5,6 shows the transient analysis of three M4 is used to give higher current for charging and different current comparators. In this propagation discharging the gates of M8 and M9 and thus delay of current comparators is presented. The propagation delay is defined as the difference of time www.ijera.com 128 | P a g e Jigyasa Singh et al Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.127-132 between the output and input when they reach the 50% of the total variation. The speed of 13T current comparator is much faster than other two comparators at 190uA and low power consumption is achieved at 1.8v. The resistor feedback is also good for high speed at low input current but the delay time is still longer than the 13T current comparator. www.ijera.com IV.COMPARISON TABLES TRANSIENT ANALYSIS FOR PROPAGATION DELAY TABLE 1: Comparison of current comparators at Vdd=1.8v Transient analysis of Traff current comparator 200uA 150uA 100uA 50uA 0A 0s 10ns 20ns 30ns 40ns 50ns 60ns 70ns 80ns 90ns 100ns I(I1) Time 2.0V 1.5V 1.0V 0.5V 0V 0s 10ns 20ns 30ns 40ns 50ns 60ns 70ns 80ns 90ns 100ns V(VOUT) Time Fig.4 Transient analysis of resistor feedback current comparator 200uA VDD= 1.8V Input current (uA) 190 195 200 205 210 215 220 225 TRAFF CURRENT COMPAR ATOR RESISTIVE FEEDBACK COMPARAT OR 13T CURREN T COMPAR ATOR propagation delay(ps) 421.466 411.7385 406.1915 396.9805 395.381 386.907 382.747 376.164 propagation delay(ps) 326.5655 347.636 354.861 356.813 359.0665 384.572 405.591 408.2525 propagatio n delay(ps) 310.1485 330.4525 340.8425 354.816 355.914 385.5225 401.9985 410.286 150uA 100uA Graph(a) of Table1 50uA 0A 0s 10ns 20ns 30ns 40ns 50ns 60ns 70ns 80ns 90ns 100ns I(I1) Propagation delay vs Input current Time 2.0V 1.6V 1.2V 0.8V 420 0.4V 0V -0.4V 0s 10ns 20ns 30ns 40ns 50ns 60ns 70ns 80ns 90ns 400 100ns V(VOUT) Time Propagation delay(ps) Fig.5 Transient analysis of 13T current comparator 2.0V 1.6V 1.2V 0.8V 380 TRAFF CURRENT 360 RESISTIVE FEEDBACK 340 13T CURRENT 0.4V 0V -0.4V 0s 10ns 20ns 30ns 40ns 50ns 60ns 70ns 80ns 90ns 100ns 320 V(VOUT) Time Fig.6 300 180 200 220 240 Input current(uA) www.ijera.com 129 | P a g e Jigyasa Singh et al Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.127-132 TABLE2: Comparison of current comparators at Vdd=2v www.ijera.com TABLE 3: Comparison of current comparators at Vdd=2.2v VDD= 2.2V TRAFF CURRENT COMPAR ATOR RESISTIVE FEEDBAC K COMPARA TOR 13T CURREN T COMPAR ATOR Input current (uA) propagation delay(ps) propagation delay(ps) propagatio n delay(ps) 190 334.436 327.1645 322.1485 195 331.4125 331.27 324.4525 200 324.0825 345.232 335.8425 205 313.954 356.4445 336.816 210 306.5965 357.155 342.914 215 299.647 358.0365 348.5225 TRAFF CURRENT COMPARA TOR RESISTIVE FEEDBACK COMPARA TOR Propagation delay(ps) Propagation delay(ps) 13T CURREN T COMPAR ATOR propagatio n delay(ps) 190 458.669 257.236 250.1485 195 455.659 298.955 284.4525 200 453.05 318.6625 315.8425 205 450.877 322.6635 315.816 210 448.6555 325.5635 320.914 215 434.4925 326.429 322.5225 220 398.7235 328.499 329.9985 220 292.1155 359.98 355.9985 225 396.5835 329.2535 331.286 225 283.0775 359.28 360.286 VDD =2V Input curren t (uA) Graph(b) of Table 2 Graph(c) of Table 3 500 470 440 410 380 350 320 290 260 230 Propagation delay vs input current 410 TRAFF CURREN T RESISTIV E FEEDBAC K 0 5 10 Propagation delay(ps) propagation delay(ps) Propagation delay vs input current 13T CURREN T 390 TRAFF CURRENT 370 350 330 RESISTIV E FEEDBAC K 310 290 270 13T CURRENT 250 0 input current(uA) 5 10 input current(uA) V.AC ANALYSIS FOR STABILITY Phase margin and Gain margin of Traff current comparator Table 1a Traff current Phase margin Gain comparator margin(db) www.ijera.com With stability 50.45590 12.73633 Without stability 42.68272 6.30394 130 | P a g e Jigyasa Singh et al Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.127-132 Table 1c 13T current comparator Phase margin and gain margin of resistor feedback current comparator Table 1b With stability Iin-Iref (mA) Phase margin Gain margin(db) 2mA(50-48) 49.99984 10.34619 4mA(50-46) 52.54245 11.33189 6mA(50-44) 53.95440 11.32349 10mA(50-40) 55.48013 11.31445 Without stability With stability www.ijera.com Phase margin Gain margin(db) 30.14507 7.72318 48.55657 12.76250 POWER DISSIPATION Power dissipation with respect to Vdd Without stability Iin-Iref (mA) Phase margin 2mA(50-48) Power dissipation(mW) 3 Gain margin(db) 10.34619 49.99984 4mA(50-46) 52.54245 11.33189 6mA(50-44) 53.95440 11.32349 10mA(50-40) 55.48013 11.31445 2.5 2 Traff current 1.5 Resistive feedback 1 0.5 13T current 0 Phase margin and gain margin of 13T current comparator 1.8 2 2.2 Vdd(v) (Without stability) 50 Graph (d) -0 -50 -100 -150 100Hz DB(V(OUT)) 1.0KHz 10KHz 100KHz 1.0MHz 10MHz 100MHz 1.0GHz 10GHz 100GHz Frequency -0d Table 1,2,3 shows the propagation delay and its graph a,b,c. Table 1a, 1b, 1c shows the stability analysis of three different current comparators. Graph (d) represents the power dissipation with respect to Vdd. -100d -200d VI. -300d -400d -500d -600d 100Hz P(V(OUT)) 1.0KHz 10KHz 100KHz 1.0MHz 10MHz 100MHz 1.0GHz 10GHz 100GHz Frequency (With stability) 50 -0 REFERENCES -50 [1] -100 -150 100Hz DB(V(OUT)) 1.0KHz 10KHz 100KHz 1.0MHz 10MHz 100MHz 1.0GHz 10GHz 100GHz Frequency -0d -100d -200d -300d [2] -400d -500d -600d 100Hz P(V(OUT)) CONCLUSION In this paper a high speed CMOS current comparator is presented using simple biasing method. In addition to less number of transistors the performance is better than both the comparators. From simulated results we concluded that 13T current comparator at 2v is much stable, delay time reduces with optimum power dissipation is achieved. 1.0KHz 10KHz 100KHz 1.0MHz 10MHz Frequency www.ijera.com 100MHz 1.0GHz 10GHz 100GHz D.J. Banks, P.degenaar, and C.Toumazou, ―A colour and intensity contrast segmentation algorithm for current mode pixel distributed edge Detection,‖Eurosensors XIX, Barcelona,2005. D.J. Banks, P.Degenaar, and C.Toumazou, ―Distributed Current-mode Image processing Filters,‖ Electronics letters, 41, pp.1201-1202, 2005. 131 | P a g e Jigyasa Singh et al Int. Journal of Engineering Research and Applications ISSN : 2248-9622, Vol. 4, Issue 5( Version 4), May 2014, pp.127-132 [3] [4] [5] [6] [7] [8] www.ijera.com H.Hassan, M. Anis, and M. Elmasry, ―MOS current mode circuits: Analysis, Design, and variability,‖ IEEE Transactions on VLSI, Vol. 13, no.8, pp. 885-898, Aug.2005. G.K. Balachandran and P.E. Allen, ―Switched current circuits in digital CMOS technology with low charge-Injection Errors,‖IEEE journal of solid-state circuits,Vol. 37, no. 10 pp. 1271-1281, oct.2002. H.Traff, ―Novel approach to high speed CMOS current comparators,‖ Electron. Lett. Vol.28, no. 3, pp. 310-312, 1992. B.-M. Min and S.-W. Kim, ―High performance CMOS current comparator using resistive feedback network,‖ Electron lett. vol. 34, no.22, pp.2074-2076, 1998. A.Tang and C.Toumazou, ―High performance CMOS current comparators,‖ Electronicslett.,vol.33,no.22,pp.1829-1830, 1997. L.Ravezzi, D.Stoppa and G.-F Dalla Betta, ―Simple high speed CMOS current comparators,‖Electronicslett.vol.33,no.22,pp .1829-1830, 1997. www.ijera.com 132 | P a g e