Hi...

Please see the attached image...I was watching signal source and signal at base of transistor

why is it that when I reduce vertical scaling the signals go down (below ground) I know I can adjust the knob to take it up but any other way??

Also..can you believe that the yellow waveform is the signal at base???? (truth)..Although Reducing base resistor brings the top part of the yellow waveform down

33k input at base with 2.2k at emitter...12v at collector and -12 through resistor to emitter

 

You mentioned scope AC coupling in the title.
So are those pictures with AC coupling or DC coupling?

 

@crutschow



Triggering on runts, for some reason, with DC coupling.

 

You mentioned scope AC coupling in the title.
So are those pictures with AC coupling or DC coupling?

Hi..On the scope..changed the channels to ac coupling

 

@crutschow

View attachment 175675

Triggering on runts, for some reason, with DC coupling.

I dont understand

 

I dont understand

You have the scope in the photo set to trigger on runts. It is also set to DC coupling.

By the way, if you put a formatted USB drive into the scope, pressing the blue Print button will save a screen shot to the drive. This is a lot better than a photo.

 

You have the scope in the photo set to trigger on runts. It is also set to DC coupling.

By the way, if you put a formatted USB drive into the scope, pressing the blue Print button will save a screen shot to the drive. This is a lot better than a photo.

hmmm..seems you got this scope...

"You have the scope in the photo set to trigger on runts. It is also set to DC coupling"...Will try to fix in 20mins..so I remove trigger on runts...but like I said, i put ac coupling on both channels

 

You have the scope in the photo set to trigger on runts. It is also set to DC coupling.

By the way, if you put a formatted USB drive into the scope, pressing the blue Print button will save a screen shot to the drive. This is a lot better than a photo.

Hi..I changed it from trigger on runts to edge...The image did not really change...The signal should not go down right?

 

It appears that the signals are swinging from 0V to -600mV

 

It appears that the signals are swinging from 0V to -600mV

yeah right...should it not go from -300 to 300?

 

yeah right...should it not go from -300 to 300?

I am not the scope, it seems to believe that in reference to its ground, the signal is almost completely negative-going. It looks as it is has a tiny positive-going part. If you are sure you are AC coupled, then it seems your circuit is producing negative output referenced to 0V.

 

I am not the scope, it seems to believe that in reference to its ground, the signal is almost completely negative-going. It looks as it is has a tiny positive-going part. If you are sure you are AC coupled, then it seems your circuit is producing negative output referenced to 0V.

lol..seems you know the scope more than I do...

Anyways, thanks...There are other interesting posts about AC coupling..will read