## 4 Simulation and Experimental Results  
### Voltage-Mode Multifunction Biquadratic Filter  
The proposed CFOA-based filer was simulated using Cadence OrCAD PSpice (version 16.6, San Jose, CA, USA), and measured using the keysight E5061B-3L5 network analyzer (Santa Rosa, CA, USA), and Agilent N9000A CXA signal analyzer (Santa Rosa, CA, USA). The CFOAs were realized using the OrCAD PSpice macro-model of the AD844 AN by Analog Devices as well as implemented in hardware using IC AD844 AN [30]. The AD844 AN supply voltages and capacitor values were selected as V\({}_{\mathrm{DD}}\) = \(-\) V\({}_{\mathrm{SS}}\) = 6V and C\({}_{1}\) = C\({}_{2}\) = 1 nF. Figures 7-11 show the simulated and measured filtering responses with the equal resistors of R\({}_{1}\) = R\({}_{2}\) = R\({}_{3}\) = 4 k\(\Omega\) for Q = 1 and f\({}_{0}\) = 39.79 kHz, respectively. Figure 12 shows the variation in the angular frequency without affecting the quality factor. In Figure 12, equal resistors with R\({}_{1}\) = R\({}_{2}\) = R\({}_{3}\) have different values of 4, 2, and 1 k\(\Omega\), resulting in Q = 1 for the HP filter and angular frequencies of f\({}_{0}\) = 39.79, 79.58, and 159.16 kHz, respectively. Next, the quality factor changes without affecting the angular frequency, as shown in Figure 13. This design is for an angular frequency of f\({}_{0}\) = 39.79 kHz with R\({}_{2}\) = R\({}_{3}\) = 4 k\(\Omega\) and only varying the value of R\({}_{1}\) as 5.6, 4, and 1.6 k\(\Omega\), resulting in Q = 0.71, 1, and 2.5 for the BP filter, respectively. To test the input dynamic range of the proposed filter, the simulation of the IBP filter as an example was repeated for a sinusoidal input signal with f\({}_{0}\) = 39.79 kHz. Figure 14 shows the time-domain of the IBP response with V\({}_{\mathrm{II}}\) = 0 and V\({}_{\mathrm{I2}}\) = V\({}_{\mathrm{in}}\) at the V\({}_{\mathrm{01}}\) output terminal, where all the resistor values are 4 k\(\Omega\). In Figure 14, the percentage of total harmonic distortion (THD) is 0.6%, when the sinusoidal input signal of an amplitude 1 V\({}_{\mathrm{P}}\) at 39.79 kHz was applied. The dependence of the IBP filter output harmonic distortion on the input signal amplitude is shown in Figure 15. As can be seen in Figure 15, when the input signal amplitude increases by 2 V\({}_{\mathrm{P}}\), its total harmonic distortion will increase by 3.2%. The intermodulation distortion (IMD) of the IBP response was studied. Figure 16 shows the dependence of the third-order IMD of IBP filter using two closely spaced tones, f\({}_{1}\) = 38.79 kHz and f\({}_{2}\) = 40.79 kHz,  
Figure 5: General equivalent circuit of the non-ideal CFOA. Figure 6: Proposed voltage-mode biquadratic filter including the parasitic elements of CFOA. Figure 11: Simulation and experimental results of HP filtering responses at V\({}_{\rm o3}\) when V\({}_{\rm i1}\) = 0 and V\({}_{\rm i2}\) = V\({}_{\rm in}\). Figure 12: Simulation and experimental results of HP filtering responses at V\({}_{\rm o3}\) when V\({}_{\rm i1}\) = 0 and V\({}_{\rm i2}\) = V\({}_{\rm in}\). Figure 10: Simulation and experimental results of IBP filtering responses at V\({}_{\rm o1}\) when V\({}_{\rm i1}\) = 0 and V\({}_{\rm i2}\) = V\({}_{\rm in}\). Figure 14: Time domain response of the IBP filter at V\({}_{\rm o1}\) when V\({}_{\rm i1}\) = 0 and V\({}_{\rm i2}\) = V\({}_{\rm in}\). Figure 13: Simulation and experimental results of BP filtering responses at V\({}_{\rm o2}\) when V\({}_{\rm i1}\) = V\({}_{\rm in}\) and V\({}_{\rm i2}\) = 0. Figure 15: Dependence of output harmonic distortion of the IBP filter on an input signal amplitude. To demonstrate the validity of the theoretical analysis, the gain and phase responses obtained through the keysight E5061B-3L5 network analyzer are depicted in Figures 18-22, respectively. In Figures 18-22, the theoretical quality factor was Q = 1 and theoretical angular frequency was f\({}_{\rm o}\) = 39.79 kHz, when the passive elements were set as C\({}_{1}\) = C\({}_{2}\) = 1 nF and R\({}_{1}\) = R\({}_{2}\) = R\({}_{3}\) = 4 k\(\Omega\).