## 3 Results
The MC analysis was run with 200 cycles, including process and mismatch variations. Regarding the PVT analysis, the process corners were fast-fast (FF), slow-fast (SF), fast-slow (FS), and slow-slow (SS). The voltage supply corners were selected at 400 mV and 500 mV, and the temperature corners were \(-10\)\({}^{\circ}\)C and \(60\)\({}^{\circ}\)C. As shown in Figure 9, the curves overlap in the case of MC and process corners, confirming the proper design of the MOS structure. The variation in the voltage corner at 400 mV results in a reduced bias current and cut-off frequency. In the case of temperature variations, the slight deviation in the cut-off frequency at \(-10\)\({}^{\circ}\)C is expected due to the sensitivity of the MOS transistor operating in the subthreshold region to temperature. The circuit offers advantages in electronic tunability. As a result, deviations caused by temperature, process variations, and voltage supply corners can be easily compensated by adjusting the filter's setting current, allowing for the readjustment of the required cut-off frequency. Figure 10a shows the transient response of the LPF when a sine wave input signal with an amplitude of 20 pA at 10 Hz is applied to the filter input, with \(I_{set}\) = 60 nA. The output signal spectrum with total harmonic distortion (THD) shown in Figure 10b confirms a low distortion of 0.16% in the output signal. Figure 11 shows the THD with various corners versus the amplitude of the input signal at 10 Hz. The nominal THD is less than 0.8% for a 40 nA amplitude of the input signal, confirming the low THD of the proposed filter. The equivalent output current noise of the LPF with various corners is shown in Figure 12. The integrated noise in the filter band from 1 to 2.66 kHz was 42.35 pA, resulting in dynamic range (DR)  
Figure 9: Frequency responses of the LPF with \(I_{set}\) = 20 nA for (**a**) MC, (**b**) process corners, (**c**) voltage corners, and (**d**) temperature corners. The proposed current-mode universal filter was compared with previously developed low-voltage universal filters in [25; 29; 31; 32], as shown in Table 4. Compared to these earlier works, the proposed filter provides the most transfer functions among the five standard filtering functions. Unlike the MISO filters in [25; 29; 31], the proposed filter does not require an input-matching condition (i.e., \(I_{in}=I_{in1}=I_{in2}=I_{in3}\)[29]) or a double-input condition (i.e., \(I_{in}=2I_{in1}=-I_{in2}\)[31]). The VCII-based filter in [32] lacks electronic tuning capability and suffers from the use of a floating resistor compared to the proposed topology. However, the universal filter in [29] achieves the lowest supply voltage and power consumption, made possible by a specialized technology (32 nm CNTFET). In addition, the filters in [25; 31] exhibit better THD and the filter in [25] demonstrates better DR compared to the proposed filter; however, they consume more power. Figure 11: The THD versus the amplitude of the input signal at 10 Hz, with \(I_{set}=60\) nA. Table 3.0 The equivalent output current noise of the LPF with \(I_{set}=60\) nA. Table 3.1 (a) Transient response of the LPF with \(I_{set}=60\) nA and (b) output signal spectrum.