New Current-Mode Filters Using Single FDCCII

The Online Journal on Electronics and Electrical Engineering (OJEEE)

Vol. (2) – No. (4)

New Current-Mode Filters Using Single FDCCII with Grounded Resistors and Capacitors Firat KACAR1 Hakan

2

KUNTMAN2

Istanbul University, Electrical and Electronics Engineering Dept., Istanbul, Turkey Istanbul Technical University, Faculty of Electrical and Electronics Eng., Istanbul, Turkey [email protected], [email protected]

Abstract-Two new current mode fully differential current conveyor (FDCCII) based multifunction filter configurations are proposed. The first proposed current mode universal filter with single input and two outputs, which can simultaneously realize current-mode low-pass (LP) and band-pass (BP), filter responses employing single FDCCII. The second proposed current mode universal filter with one input and two outputs, realize currentmode band-pass (BP) and high-pass (HP) filter responses employing single FDCCII. Moreover, each of the proposed circuits employment two grounded resistors and two grounded capacitors. We performed simulations with SPICE simulation program using 0.35^m TSMC CMOS technology. Simulation results are found in close agreement with theoretical results.

configuration. The performances of the proposed filters can be checked and simulated by PSPICE. II. FDCCII The FDCCII is basically a fully differential device as shown in Fig.1. The Y1 and Y2 terminals are high impedance terminals while X1 and X2 terminals are low impedance ones. The differential input voltage VY12 applied across Y1 and Y2 terminals is conveyed to differential voltage across the X1 and X2 terminals; i.e., (VX12 =VY12). The input currents applied to the X1 and X2 are conveyed to the Z1 and Z2 terminals that is, (Iz1 =Ix1 and Iz2 =Ix2 ).

Keywords- FDCCII, Analog integrated circuits, Biquad filter, Analog signal processing. I. INTRODUCTION Analog filters are important building blocks and widely used for continuous-time signal processing. They can find application in several areas such as communication systems, measurement and instrumentation, and control systems [1-2]. In 2000, a new active element called the fully differential current conveyor (FDCCII) was proposed [3] to improve the dynamic range in mixed-mode applications where fully differential signal processing was required. Both the use of grounded resistors and capacitors are more beneficial from the point of view of integrated circuit implementation. In the literature several voltage-mode biquad filters are presented with three inputs and one output using current conveyors [411]. FDCCII that is a relatively new active element compared to classical current conveyor [12] has been used in analog filter design [12-14]. The circuits in [12] use three FDCCIIs. Single FDCCII and five passive elements are used in [13]. The circuit of [14] employs two FDCCIIs and five passive elements. In this paper, current mode one input two outputs multifunction filter and one input two outputs universal filter have been presented. The proposed current mode biquad filters contain single FDCCII and four grounded passive elements. The first proposed filter can generate standard filter functions, LP and BP from the same circuit configuration. The second proposed filter can simultaneously realize the standard filter functions, BP and HP from the same circuit

Reference Number: W10-0040

Figure (1) The circuit symbol of the FDCCII Considering the non-idealities arising from the physical implementation of the FDCCII, its terminal relationship can be characterized by: 0 0 0 0 0 0 0  VY 1   I Y1   0 I   0 0 0 0 0 0 0 0  VY 2   Y2    IY 3   0 0 0 0 0 0 0 0  VY 3       0 0 0 0 0 0 0  VY 4   IY 4    0  V XA   1   2  3 0 0 0 0 0  I XA       0 4 0 0 0 0  I XB   V XB   1  2 I   0 0 0 0  P 0 0 0 V ZA    ZA    0 0 0 0   N 0 0 V ZB    I ZB    0 (1) where ideally β1=β2=β3=β4=1 and αN=αP=1 that represent the voltage and current transfer ratios of the FDCCII respectively. The CMOS realization of the cascode FDCCII is shown in Fig.2 [15-16].

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Vol. (2) – No. (4)

Figure (2). CMOS FDCCII implementation [16] III. PROPOSED MULTIFUNCTION FILTERS

0 

G1G 2 C1C 2

Q

1

(4)

The proposed two current-mode universal filters, employing fully differential current conveyor, are shown in Fig.3 and Fig.4. Each of the proposed circuit is composed of only FDCCII. Two of these configurations use two grounded capacitors and two grounded resistors. The first proposed current-mode multifunction filter employing one FDCCII, two resistors and two capacitors is shown in Fig.3.

The second proposed circuit can be used as either a three input single output current-mode universal filter is shown in Fig.4.

Figure (3). First proposed biquad filter employing FDCCII.

Figure (4). Second proposed biquad filter employing FDCCII.

When Y1=sC1, Y2=sC2, Ya=G1 and Yb=G2. Circuit analysis yields the following current-mode filter transfer functions:

When Y1=G1, Y2=G2, Ya=sC1 and Yb=sC2. Circuit analysis yields the following current-mode filter transfer functions:

Low-Pass: I o1 G1G 2  2 I in s C1C 2  s G1C 2  G1C1   G1G 2

Band-Pass: I o2 sC1G1  2 I in s C1C 2  s G1C 2  G1C1   G1G 2

Band-Pass: I o2 sC1G1  2 I in s C1C 2  s G1C 2  G1C1   G1G 2

(2)

G1G 2 C1C 2

(5)

(6)

High-Pass: (3)

The pole angular frequency ω0 and quality factor Q are given by

Reference Number: W10-0040

G1 C 2  C1 

I o2 s 2C1C2  2 I in s C1C2  sG1C2  G1C1   G1G2

(7)

The pole angular frequency 0 and quality factor Q are given by

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The Online Journal on Electronics and Electrical Engineering (OJEEE)

0  Q

G1G 2 C1C 2

1 G1G2C1C2 G1 C2  C1 

Vol. (2) – No. (4)

(8) (9)

IV. SIMULATION RESULTS Finally, to verify the theoretical prediction of the proposed biquad filters, SPICE simulations with 0.35um TSMC process were performed. The CMOS implementation of a FDCCII is shown in Fig. 2 [16]. The aspect ratios of the MOS transistors are given in Table i. The supply voltages were taken as ±1.3 V. Fig.3 current-mode biquad was designed for f0=10MHz by choosing R1=R2=22.5M and C1=0.5p, C2= 1pF. The Fig.5 shows the simulated and theoretical response of low-pass and band-pass of Fig.3. The current-mode biquad has been designed to provide low-pass and band-pass responses with f0=10MHz. The passive element values are chosen as R1=R2=22.5M and C1=0.5p, C2= 1pF. Fig.6 shows the simulated frequency responses for the band-pass and highpass, configurations. As can be seen, there is a good close agreement between theory and simulation. Table.1 Transistors aspect ratios for the proposed circuit Transistors L(m) W(m) M1-M6, MBP,MCP, M1N-M3N, 8.75 0.7 MAN,MKN M7-M9,M13 70 0.7 M10-M12,M16 i7.5 0.7 M14,M15,M19,M20 0.7 0.7 M17, M21, M27, M25-M26, M31-M32, 35 0.7 M1P-M3P, MAP,MKP, MBN,MCN M18, M22-M24, M28-M30 8.75 0.7 M31,M32 i05 0.7

Figure (6) Simulated frequency responses for thee circuit in Fig.4. V. APPLICATION EXAMPLE A double tuned amplifier stage is shown in Fig.7. In many tuned amplifiers it is desirable to have a flatter pass-band with steeper skirts than it is obtainable with synchronously tuned circuits. Such as pass-band can be obtained by stagger tuning, that is, tuning, the input and output circuits to slightly different frequencies [17].

Fig.7 Double tuned amplifier The poles lie on the arc of circle and the band-with B=/2 of this filter is equal to the diameter of the pole circle [17]. The transfer function of the circuit illustrated in Fig.7 is given by QP1 QP 2 H s   H 0 (10) 2  P1 2 2 P2 s  s   P1 s  s   P2 2 QP1 QP 2 where H0 is the gain factor, P1, P2, QP1 and QP2 are the pole frequencies and the quality factors of the input and output circuits of the stagger-tuned amplifier shown in Fig.7, respectively. The two resonant circuits are tuned to slightly different frequencies, which can be approximated by  B f P1  P1  f 0  sin 45 (11) 2 2  B f P 2  P 2  f 0  sin 45 (12) 2 2 The aim is to construct a double-tuned amplifier with bandpass characteristic using circuits constructed with FDCCII and passive elements. There are many applications that require a narrow band bandpass tuned amplifiers such as video signal processing, TV receivers and wireless communications stages [18]. By using the filter topology shown in Fig.3, a fourth order bandpass filter was implemented which is shown in Fig.8.

   

Figure (5). Simulated frequency responses for the circuit in Fig. 3.

Reference Number: W10-0040

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The Online Journal on Electronics and Electrical Engineering (OJEEE)

Fig.9 shows the simulated frequency response for fourth order band-pass filter.

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To obtain a filter with a center frequency of 10 MHz and a bandwith of 1.25MHz, the pole frequencies and the quality factors of circuits are chosen as fP1 = 9 MHz, fP2 = 11.5 MHz, QP1=1 and QP2=1, respectively. The resistance and capacitance values providing these properties are determined as R11=R12=22.5k and C11=0.55p, C12= 1.1pF R21=R22=22.5k and C21=0.42p, C22= 0.85pF The large signal behavior of the fourth order band-pass filter is testing by applying a 10 MHz sinusoidal signal with amplitude of 400LIA to the input. The simulated transient response of the filter is given in Fig. 10. It is obvious from Fig.8 that the filter exhibits a good large signal behavior even at high frequencies. The deviation in the actual center frequency, in the quality factor values from theoretical values is caused by the non-idealities of the FDCCII. However, grounded components enable easy fine adjustment for the center frequencies of the double-tuned amplifier.

Figure (8). A fourth-order band-pass filter realized with two FDCCII

Figure (9). PSPICE simulation results of frequency response of the fourth-order band-pass filter. VI. CONCLUSION

Figure (10). The input and output waveforms of the proposed band-pass filter of Fig. 7 for 10MHz sinusoidal input current of 400A (peak to peak)

Reference Number: W10-0040

Two new current-mode universal filters are proposed. The proposed current mode biquad contain only one FDCCII and two grounded capacitors and two grounded resistors. Moreover, both two universal biquad filters still had the following four main advantages use of all grounded capacitors and resistors, high-input impedance, no need of matching constraints and no need inverting-type current input signals. We performed simulations with SPICE simulation program using 0.35um TSMC CMOS technology. PSPICE simulation results of the filter responses are in good

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