Universal Current-Mode Biquad Employing Dual Output Current Conveyors and MO-CCCA with Grounded Passive Elements

A new universal multiple input multiple output (MIMO) type current-mode biquad employing two dual output current conveyors (DOCCII), one multiple output current controlled current amplifier (MOCCCA) and four passive grounded elements is proposed which can realize all the five basic filtering functions namely, low-pass (LP), high -pass (HP), band-pass (BP), band -stop (BR) and all-pass (AP) in current mode from the same configuration. The centre frequency


Introduction
Recently, Chunhua, Hiaguang and Yan presented two new universal multiple input single output (MISO) current-mode (CM) biquadatic filters using one MOCCCA, two grounded capacitors (GC) and two grounded resistors (GR) and realize all the five generic filter responses in CM (i.e. with current as input and current as output) [1].
The purpose of this paper is to introduce a new configuration which although uses exactly same number of active and passive components but in contrast to the circuit of reference [1] realizes a MIMO-type biquad and hence, does not require any additional hardware to duplicate/invert current inputs which is required in case of MISO-type filters of [1].
In the literature there are SIMO-type filter circuits which have three active devices but suffer from the independent tunability as in [2][3][4][5] or have more passive or active elements as in [4][5][6][7][8][9].The circuits in [10][11][12] need double inputs and outputs to realize all five generic filters.The circuit in [13] has two MO-CCCIIs and one DO-CCCII, the draw back of this circuit is the control currents oi are temperature dependent.The circuit in [14] has two MO-CCCIIs and one MOCCCA but realizes only SIMO-type biquad.

The Proposed Configuration
The proposed configuration is shown in Figure 1.
Assuming the CCIIs to be characterized by , 1,2,3 The symbolic notation of MO-CCCA is given in  If the channel lengths of M 5 -M 8 are all n times of that of M 4 , and the channel size of M 17 is n times that of M 18 , namely the output current expressions can be obtained as where K represents the current gain.It is clear from Equation (2) that the value of K can be set by I B and I A .Consider now the following special cases:

MISO Type:
When 1 2 3 4 5 are input currents and taking 03 as output current, then a routine analysis of the circuit reveals the following expression of the output curr t 03 i in terms of the five input curre nd , , , and the circuit are: LPF: when (non-inv.) and .
HPF: when and and .
Notch: when and .
APF: when 2 3 4 and or and .

SIMO Type
(open circuited) then, the various filter responses realized are given by: HPF: BPF: APF: The various parameters of the realized filters are given by From Equation ( 9 From the above, the active and passive sensitivities of the transfer function are given as The active and passive sensitivities of  and are o Q found to be in the range , and the circuit, thus, enjoys low sensitivities.

Simulation Results
To verify the validity of the various modes of operation of the proposed configuration, circuit simulation of the current mode filters (MISO and SIMO) have been carried out using the CMOS CCII implementation with multiple outputs shown in Figure 3 (as in [15], modified from [16]).
The model parameters of n-channel and p-channel MOSFETs are given in [17], whereas aspect ratios of the CCII MOSFETs are shown in . The frequency responses of LPF, BPF, HPF, Notch and APF (theoretical and simulation) are shown in Figure 4.
To test the input dynamic range of the proposed filters, the simulation of the band-pass filter as an example has   been done for a sinusoidal input signal at o 1 MHz f  .Figure 5 shows that the input dynamic range of the filter response extends up to amplitude of 105 μA without significant distortion.The dependence of the output harmonic distortion on the input signal amplitude is illustrated in Figure 6.For input signal amplitudes lower than 110 μA, the total harmonic distortion (THD) is of the order of less than 1% after that rapidly increasing is occurred.The obtained results show that the circuit operates properly even at signal amplitudes of about 120 μA and THD less than 4%.
To achieve the SIMO type filters with o 1 f  MHz and quality factor of , the component values were selected , puts respectively, and I A and I B denote DC bias currents.

Figure 2 (
b) is a CMOS realization of MO-CCCA.Here I i denotes the input signal; I o1 , I o2 , I o3 are the three output currents, respectively.
), the centre frequency o  can be set by varying R 1 without disturbing o o Q  .The o can also be set by I B and I A without disturbing o Q  .Therefore, the biquad filter has independent tenability for the o  and .o

Figure 4 .
Figure 4. PSPICE Simulation results (a) Gain response of LPF, BPF, HPF and Notch; (b) Gain and Phase response of APF.

Figure 7 .
Figure 7. PSPICE Simulated gain responses of LP, BP, HP and Notch for SIMO type filter.

Figure 8 .Figure 9 .
Figure 8. Simulation results for control of Q o while keeping f fixed (1 MHz) for band pass filter.o

Figure 10 .
Figure 10.Simulation results for control of Q o and gain while keeping f o = 1 MHz fixed for band pass filter.

Table 1 ,
and aspect ratios of the MO-CCCA MOSFETs are shown in Table2.To achieve the MISO type filters with o  MHz and quality factor of Q o = 1, the component values were selected 