# High-Input Impedance Voltage-Mode Multifunction Filter
## 4 Simulation and Measurement Results  
In order to confirm the theoretical study, the proposed circuit of Figure 2 was simulated using the AD844 macro-models of OrCAD PSpice version 17.2 and was experimented using commercial AD844 AN of analog devices. The power supply voltage was given as \(\pm\)6 V. The passive component values of the Figure 2 are given by R1 = R2 = R3 = 4 k\(\Omega\) and C1 = C2 = 1 nF for the center frequency of f0 = 39.79 kHz. Figures 4-6 show the simulation and experimental gain-frequency and phase-frequency voltage responses for the NLP, IBP, and NBS filters of Figure 2, respectively. In the simulated NLP voltage response of Figure 4, the center frequency f0 is 38.9 kHz, which is \(-\)2.23% different from the theoretical value. In the simulated IBP voltage response of Figure 5, the center frequency f0 is 38.5 kHz, which is \(-\)3.24% different from the theoretical value. In the simulated NBS voltage response of Figure 6, the center frequency f0 is 38.9 kHz, which is \(-\)2.23% different from the theoretical value. Figure 7 shows the different Q-values of IBP voltage response and the tunable Q-values, Q = 0.71, 1, and 2.5 are obtained without affecting the f0 parameter. In Figure 7, R2 = R3 = 4 k\(\Omega\), C1 = C2 = 1 nF, and only vary the resistor R1 as 5.6, 4 and 1.6 k\(\Omega\). It is found that the total power consumption of the simulation is 255 mW. Figures 8-10 represent the experimental frequency responses for the NLP, IBP, and NBS voltage responses of Figure 2, respectively. In the measured NLP voltage response of Figure 8, the center frequency f0 is 41.364 kHz, which is 3.96% different from the theoretical value. In the measured IBP voltage response of Figure 9, the center frequency f0 is 40.729 kHz, which is 2.36% different from the theoretical value. In the measured NBS voltage response of Figure 10, the center frequency f0 is 41.036 kHz, which is 3.13% different from the theoretical value. The experimental gain-frequency voltage responses of the IBP filter with difference Q-values is shown in Figure 11. Figure 12 shows the experimental measurement result of the IBP transient response of the 40 kHz frequency and 2 V peak voltage of input voltage signal. It can be seen from the simulation and experimental results that they are consistent with the theoretical values.  
Figure 4: Gain-frequency and phase-frequency voltage responses of the non-inverting low-pass (NLP) filter.  
Figure 5: Gain-frequency and phase-frequency voltage responses of the inverting band-pass (IBP) filter.  
Figure 6: Gain-frequency and phase-frequency voltage responses of the non-inverting band-stop (NBS) filter.  
Figure 8: Experimental gain-frequency and phase-frequency voltage responses of the NLP filter.  
Figure 7: Gain-frequency voltage responses of the IBP filter with different Q-values by changing resistor R\({}_{1}\).  
Figure 10: Experimental Gain-frequency and phase-frequency voltage responses of the NBS filter.  
Figure 9: Experimental Gain-frequency and phase-frequency voltage responses of the IBP filter.  
The 1-dB compression (P1 dB) point is a key metric to determine the linear region of the circuit's operation. This point represents that the input power reduces 1 dB gain from the normal linear gain specification. In general, there is nonlinearity in the transfer functions of all electronic circuits, and nonlinear distortion occurs. Hence, the third-order intercept (TOI) point measurement is a good indicator of the depth of distortion created by intermodulation products. Figures 13 and 14 show the measurement results of the P1 dB and the TOI point, respectively. The measured input P1 dB point is 18.8 dBm and the measure TOI point is 29.04 dBm.  
Figure 11: Experimental gain-frequency voltage responses of the IBP filter with difference Q-values by changing resistor R\({}_{1}\).  
Figure 12: Experimental measurement result of the IBP transient response for frequency 40 kHz and 2 V peak voltage of input voltage signal.