Second Lab

Capacitance of diodes

From data sheet, the Cj0 of D1N4002 and D1N4004 are both 15pF.

Figure 1: datasheet of diodes

For Pispice, Cj0 of D1N4002 is 51.17pF.

According to lab results, Cj0 of D1N4002 is 61.8pF.

Cj0 of D1N4004 is 58 pF.

We do not know why there is a huge difference among the Cj0 of Pspice, datasheet and measurement.

Resonance frequency

According to theory, the resonance frequency is 1/2pi*sqrt(LC).

For D1N4002, C(measurement)= 61.8pF, L=39mH.

The resonance frequency is 102.516KHz.

When the amplitude of the source voltage is 50mV and the resistor is 100KΩ, the lab results are shown in the following table.

The resonance frequency is 97.16KHz.

Frequency(Hz)	VR(mV)
10	5
50	5
100	5
500	5
1000	5.4
5000	7.2
8000	10.8
10000	12.6
30000	20.6
50000	23.4
80000	30.4
97160	49.2
100000	21.2
300000	19
1000000	17.9

Table 1: Resonance frequency for D1N4002

Figure 2: Resonance frequency for D1N4002

This figure is similar to the Pspice simulation

Figure 3 shows the resonance frequency of D1N4002 using Pspice

Figure 3: Resonance frequency for D1N4002 using Pspice

For D1N4004, C(measurement)= 58pF, L=39mH.

The resonance frequency is 105.821KHz.

When the amplitude of the source voltage is 50mV and the resistor is 100KΩ, the lab results are shown in the following table.

The resonance frequency is 99.13KHz.

Frequency(Hz)	VR(mV)
10	5
50	5
100	5
500	5
1000	5.2
5000	7
8000	10.4
10000	12.4
30000	18.2
50000	21
80000	26.2
99130	42.6
100000	42.2
1000000	15.6

Table 2 : Resonance frequency for D1N4004

Figure 4: Resonance frequency for D1N4004

Resonance frequency shift

According to theory, resonance frequency should not change as the value of the resistor change.

But, in reality, resonance frequency increases with the value of the resistor increasing.

For D1N4002, when VPP of the source voltage is 100mV, the lab results are shown in the following table.

Resistor(Ω)	Resonance frequency(KHz)	VR(mV)
10000	89.6	25.6
55000	94.63	48
100000	95.92	49.6

Table 3: Resonance frequency change with resistor changing

This result compromises with the Pspice simulation.

Resistor(Ω)	Resonance frequency(KHz)	VR(mV)
55000	109.548	49.824
100000	112.074	49.896
1000000	122.775	49.991

Table 4: Resonance frequency change with resistor changing using Pspice

Chaotic phenomenon

Chaotic circuit is a dynamic system caused by nonlinear component.

If the voltage of the source is fit, hovers around a limit ellipse can be observed.

The orbits of hovers never intersect.

Figure 5:D1N4002 partly chaotic

Figure 6: D1N4002 totally chaotic at the frequency of resonance frequency

Figure7: Partly chaotic D1N4004

D1N4004 completely chaotic at the frequency of chaotic frequency

 The following radio shows the circuit starts becoming chaotic.