LTspice simple syntax problem

[cupoftea]

Hi,
How do i make the time of a "Pulse" source equal to the voltage of a node in LTspice?
The attached LTspice wont work. Do you know how to solve?

 

[FvM]

SPICE parameters are static, not dependent on voltages and currents. You can vary parameters per run but not during run.

To generate dynamical variable pulse times, use pwm generator circuits or similar.

 

[BradtheRad]

I've experimented (simulated) with a circuit similar to sample-n-hold.

1) Expose a capacitor to an incoming voltage charging it to that voltage.
2) Have it turn on a transistor.
3) The cap discharges as it biases the transistor to generate a pulse.
4) The pulse length is roughly comparable to the original voltage.

--- Updated Feb 24, 2024 ---

Components need to be adjusted: capacitor, discharge resistance, threshold levels, etc.

 

[KlausST]

How do i make the time of a "Pulse" source equal to the voltage of a node in LTspice?

Isn´t this the classical analog way of generating PWM?

comparator:
* IN1 = triangle
* IN2 = control voltage
* OUTPUT = pulses where the pulse width linearely depends on control voltage

Klaus

 

[FvM]

Isn´t this the classical analog way of generating PWM?

Sure. An LTspice pulse width modulator block would use ideal ramp generator and a behavioral comparator instead of RC circuit and OP.

--- Updated Feb 25, 2024 ---

Also interesting in this regard https://github.com/kanedahiroshi/LTspiceControlLibrary

 

[D.A.(Tony)Stewart]

Use the Arbitrary voltage source to modulate another with any formula.