I am trying to simulate a simple circuit using a simulation program like SPice. In the begining of the circuit I have a Pulse train voltage source, later it is connected to a normal LPF. the voltage source frequency is set as 1KHz, my question is how to increase this frequency? The only options that I have is to change the cycle time and the voltage. If I set cycle time= 1ms and the voltage= 5v, the frequency will be 1KHz.
If I change the time to 0.5ms, the result will be 5v for 0.5ms and the rest is 0. (the second cycle will not start after 0.5ms, so the frequency is same 1KHz).
Strange!! How to increase the frequency of the voltage source?

 

I use ltspice, but I think it is about the same. You should be able to insert a voltage source into your circuit then either make it ac or dc. If you choose ac you just put in the frequency when you right ckick the voltage source. If you use DC (pulse) you need to go advanced and put in rise time, fall time, time on, and period.

 

hi,
If your Spice has a LM331 model , you can use that for a frequency sweep.
This image uses LTSpice models to build a hierarchical model of the LM331

The V3 source gives approx 1K/Volt frequency increase.

E

 

Hi Eric.

 

Post you circuit diagram and we can better help you.

Voltage sources can be either DC, Large-Signal (Pulse, Sine, PWL, etc. ) or Small-Signal AC.

The Large-Signal source in used in transient analysis where the circuit non-linearities are included, such as transistor effects and the limits imposed by the circuit voltages.

The Small-Signal AC uses a linear model for everything so ignores actual circuit voltage limits. It is used when you want the input/output sine-wave AC transfer function over a frequency range, giving gain and phase versus frequency from input to output.