5.19 Frequency domain simulation

Apart from time-domain simulation, Alecsis simulator also performs the frequency domain simulation. Following examples illustrate this feature.

Implementation of the frequency domain simulation implies extensions of the AleC++ language. Command ac specifies frequency domain simulation. Independent sources vac (voltage) and cac (current) provide excitation. Since AleC++ is extension of the C++, values are treated as objects. In this manner, for frequency domain simulation, they have been added new properties: amp (amplitude), phase (phase), real (real part) and imag (imaginary part), with output->phase specifying the phase of the output .

As a simulation example for passive circuits, a ten stage crystal band-pass filter shown in figure 5.55.a has been simulated. Obtained amplitude characteristic is shown in figure 5.55.b.

As an example for simulation of active circuits, a simple one-stage MOS amplifier has been simulated. Figure 5.56.b shows the simulation results for variations of the supply voltage.

Fig. 5.55.a: Ten-stage crystal band-pass filter

Fig. 5.55.b: Amplitude characteristic

Fig. 5.56.a: Simple MOS amplifier

Fig. 5.56.b: Amplitude characteristic for supply variation


vac Vin;
mosfet m1;
Vin(input1, 0) {amp=1mV; phase=0rad;};
m1(d, g, s, 0) {model=my_nmos; l=2u; w=6u; };


plot{node d->amp;}
ac {fscale = 2; fstart = 1; fstop = 100G; fnum = 100;}