## 1 Introduction
The circuit joins one more important advantage of orthogonal controllability of the resonance angular frequency (\(\omega_{\mathrm{o}}\)) and quality factor (Q) and enables implementation of all standard filtering functions in CM and TAM, but a component-matching condition is still needed to realise the AP response in TAM. This study proposes a new configuration for realising electronically tunable mixed-mode universal biquadratic filters. The proposed circuit employs three CCCCTAs and two grounded capacitors. When operating in CM/TAM, the circuit can simultaneously realise LP, BP and HP filtering responses. The BS/AP filtering responses are also obtained with interconnection of the relevant output currents without any component-matching conditions. When operating in TIM, the circuit can simultaneously realise LP, HP and two BP filtering responses. The LP, BP, HP and BS/AP filtering responses are also obtained simultaneously in VM operation. The advantages of the proposed circuit are the following: (1) resistorless and electronically tunable structure; (2) simultaneous realisation of three generic filtering responses in all the four possible modes; (3) capability to realise BS and AP filtering responses in the VM, CM and TAM without critical component-matching conditions; (4) low-input and high-output impedances for current signals; (5) high-input impedance for voltage signal; (6) use of only grounded capacitors; (7) orthogonal control of the parameters Q and \(\omega_{\mathrm{o}}\) of the filter; (8) independent control of the VM filter gains without affecting the parameters Q and \(\omega_{\mathrm{o}}\); and (9) low active and passive sensitivity performances. Tables 1 and 2 compare the proposed circuit with previously reported mixed-mode biquad circuits. It is interesting to note that the proposed circuit only employs three multiple-output CCCCTA active components and two grounded capacitors. Regarding the CCCCTA-based biquads proposed in [26; 27], the proposed circuit does not require component-matching conditions to realise the AP response in CM and TAM, and two more standard filter signals can be obtained in VM. Another attractive feature is the independent tunability of the VM filter transfer gain constants without affecting the parameters \(\omega_{\mathrm{o}}\) and Q. Moreover, the CM filter enjoys a low-input and high-output impedance feature, which is a desirable feature for the CM cascading. Since the proposed circuit does not require external resistors and uses only grounded capacitors, it is suitable for integrated circuit (IC) implementation. Tables 3 and 4 compare the main features of the proposed circuit with those of previous CCCCTA-based works [26; 27]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Filters** & **No. of Active Elements** & **No. of Passive Elements** & **Composed of Equivalent Active Elements** \\ \hline
[13] & 7 CCII & 2C + 8R & 7 CCII \\
[14] & 3 CCII & 3C + 4R + 2 switch & 3 CCII \\
[15] & 4 CFOA & 2C + 9R + 1 switch & 4 CFOA \\
[16] & 3 DVCC & 2C + 3R & 3 DVCC \\
[17] & 3 DDCC & 2C + 4R & 3 DDCC \\
[18] & 1 FDCCII & 2C + 3R & 2 DDCC \\
[19] & 3 FTFN & 2C + 3R & 3 \(\times\) 2 CFOA \\
[20] & 7 OTA & 2C & 7 OTA \\
[21] & 5 OTA & 2C & 5 OTA \\
[22] & 4 OTA & 2C & 4 OTA \\
[23] & 4 MOCCCII & 2C & 4 MOCCCII \\
[24] & 5 MOCCCII & 2C & 5 MOCCCII \\
[25] & 4 MOCCCII & 2C & 4 MOCCCII \\
[26] & 3 CCCCTA & 2C & 3 \(\times\) (1 CCCII + 1 OTA) \\
[27] & 3 CCCCTA & 2C & 3 \(\times\) (1 CCCII + 1 OTA) \\ this work & 3 CCCCTA & 2C & 3 \(\times\) (1 CCCII + 1 OTA) \\ \hline \hline \end{tabular}  
* \({}^{1}\) CCII: current conveyor; CFOA: current feedback operational amplifier; DVCC: differential voltage current conveyor; FDCCII: fully differential current conveyor; FTFN: four-terminal floating nullor; OTA: operational transconductance amplifier; MOCCCII: multiple-output current controlled conveyor; CCCCTA: current controlled current conveyor transconductance amplifier.  
\end{table} 
Table 1: Comparison of previously reported mixed-mode filters. \({}^{1}\)