## 6 Simulation Results  
To verify the theoretical analysis of the proposed circuit, an H-Spice simulation with Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 \(\upmu\)m process was performed. Figure 5 shows the CMOS schematic of a MO-CCCCTA [34], where the multiple outputs are multiple current mirrors. The aspect ratios (\(W/L\)) of the MOS transistors of Figure 5 are given in Table 3. The supply voltages are \(V_{DD}=-V_{SS}\) = 0.9 V. In order to get the \(f_{o}\cong\) 2.12 MHz oscillation frequency of the sinusoidal output waveforms, the values of the active and passive components have been chosen as \(g_{m1}=g_{m2}\) = 133.33 \(\upmu\)A/V (\(I_{B}\) = 42.9 \(\upmu\)A); \(R_{X1}=R_{X2}\) = 7.5 k\(\Omega\) (\(I_{S}\) = 3.96 \(\upmu\)A); \(C_{1}\) = 10.1 pF; and \(C_{2}\) = \(C_{3}\) = 10 pF. The variation of the transconductance value changes \(I_{B}\) from 1.5 \(\upmu\)A to 210 \(\upmu\)A as depicted in Figure 6. When the bias current is larger than 160 \(\upmu\)A, the transconductance gain is decreased as the transistors (M20, M21) enter the linear region from a saturation region. The maximum transconductance gain is approximately 256 \(\upmu\)A/V. In other words, when the bias current is larger than 160 \(\upmu\)A, the internal construction transistors of the MO-CCCCTA operates in the linear region, which will result in the distortion of the output swing. The steady state output waveforms of the quadrature voltages are shown in Figure 7 and the quadrature currents are shown in Figure 8. The oscillation frequency, \(f_{o}\), of the simulation results is equal to 2.11 MHz, which is consistent with the theoretical analysis. The total harmonic distortion (THD) analysis of the \(V_{o1}\), \(V_{o2}\), \(I_{o1}\) and \(I_{o2}\) are summarized in Tables 4-7, respectively. Furthermore, the output current, \(I_{o3}\), can be used as an AM or ASK signal generator, when the amplitude of the input bias current, \(I_{B2}\), is applied to a sinusoidal signal, a triangular signal, or a pulse signal. Thus, the proposed oscillator can generate either AM or ASK signals without additional elements. Figures 9 and 10 show the simulated results of the proposed circuit serving as an AM signal generator, when the input bias current, \(I_{B2}\), is applied to a sinusoidal signal or a triangular signal with a 200-kHz frequency. Figure 11 shows the simulated results of the proposed circuit serving as an ASK signal generator when the input bias current, \(I_{B2}\), is applied to a pulse signal with a 200-kHz frequency. Figure 5: The internal construction of MO-CCCCTA. Figure 6: Variation of transconductance with bias current. Figure 8: Simulated quadrature current outputs \(l_{01}\) (blue) and \(l_{02}\) (red). Figure 7: Simulated quadrature voltage outputs \(V_{o1}\) (blue) and \(V_{o2}\) (red). Figure 9: Simulated result of operation as an AM signal generator when \(l_{B2}\) is the applied sinusoidal signal. Figure 11: Simulated result of operation as an ASK signal generator when \(I_{B2}\) is the applied pulse signal. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Transistors** & \(L\) (\(\mu\)m) & \(W\) (\(\mu\)m) \\ \hline M1–M2 & 0.35 & 7 \\ M3–M4 & 0.35 & 14 \\ M5–M10 & 0.5 & 20 \\ M11–M17, M20, M21 & 0.5 & 10 \\ M18, M19, M27 & 0.8 & 8 \\ M22–M26 & 0.8 & 25 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The aspect ratios of the CMOS transistors in MO-CCCCTA implementation. Figure 10: Simulated result of operation as an AM signal generator when \(I_{B2}\) is the applied triangular signal. The MO-CCCCTA is not an off-the-shelf component but can be built by commercially available integrated circuits (ICs). For testing the proposed oscillator, Figure 12 shows an equivalent method similar to Figure 3 by using ready-to-use ICs, which include the operational amplifiers of AD844s