Hello there!
I have been tasked to design a flashing light at 2Hz. I am hoping the design I made will work but I can't seem to simulate this design on LTSpice.
If you guys have any tips or any idea if this design will work, that would be much appreciated.

P.S. The Op amp I will be using is an LMV301 (or something similar) Not an AD8613.

 

Hello,

The output of the opamp is not connected.
The supply voltage (3 Volts) is likely to low to drive the mosfet.



Bertus

 

Hello,

The output of the opamp is not connected.
The supply voltage (3 Volts) is likely to low to drive the mosfet.

View attachment 201718

Bertus

My bad, Yeah I forgot to connect it haha. OK well how about a BSS138 low feild effect N-channel fet?

 

MOD NOTE: Moved to Homework Help.

 

Why are you powering your opamp from the signal across the capacitor?

Explain your thinking on how you expect your circuit to work over the course of one cycle.

 

Hello,

The bss138 has a threshold voltage of about 1.3 Volts @ 1 mA.
Read the datasheet for all properties of the mosfet.

What leds are you using?
It can be that the leds will not light at all at the 3 Volts supply.

Bertus

 

Hello,

The bss138 has a threshold voltage of about 1.3 Volts @ 1 mA.
Read the datasheet for all properties of the mosfet.

What leds are you using?
It can be that the leds will not light at all at the 3 Volts supply.

Bertus

I am basing it of of this schematic that my work has made. I have attched data sheet of LEDs too

 

Why are you powering your opamp from the signal across the capacitor?

Explain your thinking on how you expect your circuit to work over the course of one cycle.

I am trying to adapt this circuit my work has made. As you can see on the circuit pins 2 and 5 are covered by c3

 

I originally thought that C3 was also tied to one of the op amp inputs, making it a timing capacitor. But I see that it isn't. What is the purpose of R1? In the original schematic, it would appear to be part of the control circuitry on the left hand side that responds to signals between the pairs of input ports on the left edge. But that resistor is less than half the size of yours. Why change the value? Why leave it in if you are getting rid of the rest of that part of the circuit?

The presence of that resistor is going to inject a fair amount of noise into the power supply and also your reference. That may or may not be critical for your purposes.

Speaking of which, what ARE your purposes? Why are you designing this circuit? Other than flashing some LEDs at 2 Hz, what is important? How close to 2 Hz? How stable? How important is the duty cycle? This may be a perfectly reasonable approach or an approach guaranteed to fail depending on the answers to questions like those.

 

Your capacitor values are HUGE (Farads).
The generic FET model in the sim should be replaced by a real-world FET model.

 

Had you connected the output of the IC to the gate of the FET and had enough time to do a transient sweep, your waveforms could have looked like :



I don't know how long LTSpice would take to sweep 6 million seconds.