Hey guys,
I'm designing a sawtooth generator and I want to use a 555 timer and a integrator.
I'm testing it at low frequency but my goal is to reach 2MHz at the end. I can't figure out why but my integrator is giving me nothing good.
Would anyone have an idea of what's going on here ?

Thanks a lot guys !

 

Reliable, very high frequency Circuits, do not play by the "normal" rules.
A 555-Timer is not the chip to use for ~2-Mhz.
You need to start-out by stating what problem You are trying to solve.
What do You want the end-product to do ?
.
.
.

 

Reliable, very high frequency Circuits, do not play by the "normal" rules.
A 555-Timer is not the chip to use for ~2-Mhz.
You need to start-out by stating what problem You are trying to solve.
What do You want the end-product to do ?
.
.
.

Hi,
Thanks for the reply.

I'm designing a boost converter with a voltage compensator. That compensator works fine. I've been simulating with a source to generate the sawtooth waveform but now I want to design an analog circuit to do so because I obviously can't have a generator in my final product.
Thanks a lot!

 

Are you sure V3 is set up properly?

EDIT:

So after zooming I can see the voltages are correct.

Below some solutions are offered but no explanation.

So basically the 555 is incapable of pulling the inverting input voltage below that of the non-inverting input so the amp output remains pinned to the negative rail. (or close to the rail)

 

Would anyone have an idea of what's going on here ?

Please include your spice file.
Connect the (+) input of the opamp to 1/2 of the 10V supply. Or just connect to +5V.

 

Please include your spice file.
Connect the (+) input of the opamp to 1/2 of the 10V supply. Or just connect to +5V.

Hi,
Here it is . Thank you for the feedback !

 

hi ach,
This is what I see.
E

@acheriti

Check your Colour for plotting, are you plotting Black on Black.??

 

hi a,
This is 2MHz, it works with a 555 TTL, but the waveforms are better with a 7555 CMOS.
E
@acheriti

Modified your circuit, added the asc file

 

You need to start with a symmetrical squarewave with 50% mark space ratio, otherwise it has a net DC content, which will quickly get integrated and the output will hit the supply rail.
The NE555 is only working because it’s not quick enough to be producing the mark space ratio that the timing resistors have set.

 

hi I,
If your post is for me, I am already aware of the Integrator limiting at the supply voltage.

As yet, as usual, we have no idea what the TS has in mind for this circuit.
E