UNIVERSAL CURRENT-CONTROLLED CURRENT-MODE FILTER WITH THREE-INPUTS AND ONE-OUTPUT USING THE CURRENT CONTROLLED CONVEYOR

A new current-mode universal filter is proposed. The filter uses five current-controlled current-conveyors (CCCII) and can realise lowpass, highpass, bandpass, notch and allpass responses. The parameters ω0, (ω0/Q0) can be controlled by adjusting the bias currents of the CCCIIs. The proposed circuit enjoys low sensitivities.

While programmability can be achieved by combining current conveyors and OTAs [19], the recently introduced second-generation current-controlled conveyor (CCCII) [20] allows current conveyor *Corresponding author.34 M.T. ABUELMA'ATTI AND M. A. AL-QAHTANI applications to be extended to the domain of electronically program- mable functions.Figure l(a) shows the electrical symbol of the CCCII+.Using two CCCII+ and two grounded capacitors, a voltage-mode bandpass filter was reported [20] and a current-mode bandpass filter was reported [21].No attempt has been reported, so far, to present universal second-order current-mode filters using the

PROPOSED CIRCUIT
The proposed circuit is shown in Figure l(b).Using standard notations, the CCCII+ can be characterised by iy O, V Vy + Ri and i +i, where R VT/2Io, VT is the thermal voltage and Io is the bias current of the CCCII.Routine analysis yields the current transfer function which can be expressed by Now, a current-mode bandpass filter is obtained if we choose A current-mode lowpass filter is obtained if we choose 12 13 0, thus ILv 1 /C C2Rx Rx2 I1 s 2 + s(Rx3/C2Rx2Rx4) -+-((Rx3/Rxs)/C1C2RxlRx2) (3) A current-mode highpass filter is obtained if we choose 11 I2 0, thus 2 /HP S 13 S 2 + S(Rx3/C2Rx2Rx4) + ((Rx3/Rxs)/C1C2RxlRx2) (4)   current-mode notch (bandreject) filter is obtained if we choose 0, I 13 I and Rx3 RxS, thus And a current-mode allpass filter is obtained if we choose 11 13 -12 Ii and Rx3 Rx4 Rx5, thus From Eqs. (2-6) the parameters Wo and wo/Qo can be expressed as Rx3/Rx5 (7 From Eqs. (2-4) it can be seen that the high frequency gain of the highpass filter is equal to unity, the dc gain of the lowpass filter is equal to Rx5 GLP Rx3 (9) and the bandpass gain at Wo is equal to Rx4 Gap (

10) Rx3
From Eqs. (7-10) it can be seen that the paramter Wo can be adjusted by controlling the resistance Rxl, that is the bias current lol, without disturbing the parameters wo/Qo, the lowpass gain GLp and the bandpass gain, Gap.Moreover, the parameter wo/Qo can be adjusted by controlling the resistance Rx2, that is the bias current lo2, without disturbing the parameter Wo, the 10wpass gain, GLr, and the bandpass gain Gap.Furthermore, the bandpass gain can be adjusted by controlling the resistance Rx4, that is the bias current lo4, without disturbing the parameter Wo.However, this will disturb the parameter wo/Qo.Finally, the lowpass gain can be adjusted by controlling the resistance Rx5, that is the bias current lo5, without disturbing the  tA.
parameter wo/Qo.However, this will disturb the parameter Wo.A possible strategy for adjusting the parameters O.;o, wo/Qo and the bandpass or the lowpass gains is therefore as follows" first the resistance Rx4 or Rx5 that is the bias current Io4 or Io5 is adjusted to control the bandpass gain Gap or the lowpass gain GLp, then the bias current Iol is adjusted to control the parameter a;o and finally the bias current lo2 is adjusted to control the bandpass gain.From Eqs. (7 and 8) it is easy to show that the sensitivities of the parameters Wo and Qo are (c) 1" lol 1 uA 2" 1ol 10 uA 3" Io1:100 uA
FIGURE (a)Electrical symbol of the plus-type current-controlled current conveyor.(b) Universal current-controlled current-mode filter.

CCCII 4 -
and grounded capacitors only.It is the purpose of this paper to present such a configuration.