But what these two circuits differ in is the input and output impedance levels, although the sign of the transfer function http://www.selleckchem.com/products/Perifosine.html also differs. The circuit of [1] does not exhibit high input impedance and low output impedance contrary to the latest ones [16]. Now, comparing the circuit’s relative complexities, it is to be mentioned that buffered output DXCCII [16] is complex when compared to a CCII?. Thus, keeping in view the relative complexity and features realized in two extreme time separated work [1, 16], an optimum solution is desired, which is missing in the literature ([1�C16] and cited therein).The RC network in both [1] and (Filter-4 of [16]) is the same, but the active element is quite different. For this particular passive network, DXCCII is not a necessity, as simpler alternatives are possible.

The basic scheme used in [1] is shown in Figure 1, which requires three voltage followers (VFs) and one current follower (CF) if all the features of [16] are also to be retained. Alternatively, a simpler circuit would require two voltage followers (one of them with two outputs) and one current follower. Now, lot of circuit complexity of ��DXCCII with buffered output�� used in [16] becomes redundant for realizing the goal. A simpler approach would only demand an extra-Xstage, resulting in a new active element, named EX-CCII (with buffered output), as DX is already reserved for dual-X CCII. As compared to a DXCCII, an EX-CCII has bothX1 andX2 terminal voltage of same polarity as that of terminalY. The symbol of the newly introduced active building block is shown in Figure 2, with its defining equation asFigure 1Basic scheme for all-pass section.

Figure 2Symbol of EXCCII VW=VZ.(1)With a view of the??VX1=VX2=VY,IZ?=?IX1,??with buffered output.IY=0, preceding developments, an optimum all-pass filter solution is now proposed in Figure 3. The voltage transfer function for the circuit isT(s)=s?1/R1Cs+1/R2C.(2)Figure 3New proposed all-pass filter circuit.Using matched resistors (valueR), (2) above reduces toT(s)=s?1/RCs+1/RC.(3)The phase function for the transfer function of (3) is��=180��?2tan?1(��RC).(4)The circuit of Figure 3 considering [1, 16] is better than the latest one (Filter 4 of [16]) if circuit complexity is compared. Unlike DXCCII with buffered output, the new EXCCII-based circuit does not requireXnstage.

As far as the output buffer stage is concerned, it is the same as in [16], thus, making the new solution (Figure 3) complex in comparison to [1] but with additional advantages over [1] as already mentioned. This is what makes the proposal an optimum one keeping in view the two most time separated work [1, 16] by the author. Based Brefeldin_A on the realization of the circuit using VFs and CFs, the one in [1] requires a VF and a CF each. Similarly, the Filter-4 in [16] uses two VFs, two CFs, and an inverting-VF (IVF). It is to be noted that the new proposal is still an unreported circuit in the available literature on the topic [1�C33].