Voltage decay cross Inductor

[ChuckOliveira]

I have this very simple RL circuit and I cannot see to plot the decay voltage across the inductor. Time constant is 50ns. Any ideas? Thanks

Vdd dd gnd DC 3
R1 dd gnd 1000000
R2 dd node 1000000
L1 node gnd 100mH ic=3

* Analysis
.options post
.TRAN 50n 500ns
.PRINT TRAN v(node)

.end

 

[FvM]

1. R1 is functionless because it's connected parallel to voltage source.
2. Time constant is L1/R2 = 100 ns
3. To see varying voltage in simulation, initial transient simulation must be skipped with uic option in .tran command.
4. Component values are not feasible in real world, it's a purely theoretical setup.

 

[D.A.(Tony)Stewart]

All inductors have DCR or dc resistance. In small sizes 2~100 <DCR/L < 1000~7000 typ.

Thus your circuit works in series but is very high impedance and very low current. With such a high inductance we would expect winding capacitance to resonate with L much lower than the BW of your 50 ns signal BW=0.5/tau = 10MHz. SRF will be more like 10kHz.

This is not practical.

but this is

 

[FvM]

Assuming ideal components, you get the below waveform.

As stated, the results are unrealistic because you can't make a 100 mH inductor without winding capacitance.