JfetBOZ mods

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#225
I usually measure Vi and Vo as shown for unbalanced-in and balanced-out at different frequencies:

V gain = Vo/Vi x 2

Then, I could reasonably estimate what is the V-gain at each frequency
and how the gain curve varies along the frequency axis.



:darkside:


Hmm . . . the forum refuses attachement of my sketch having size of 37kB. Why . . . ? Because there are too many OTs?
 
#226
Babowana said:
I usually measure Vi and Vo as shown for unbalanced-in and balanced-out at different frequencies:

V gain = Vo/Vi x 2

Then, I could reasonably estimate what is the V-gain at each frequency
and how the gain curve varies along the frequency axis.



:darkside:


Hmm . . . the forum refuses attachment of my sketch having size of 37kB. Why . . . ? Because there are too many OTs?
Click to expand...

I've noticed that PNG graphics can be physically larger than the other formats. Try that.

What if you have balanced in and single-ended out?
 
#229
I'm trying again . . .

I usually estimate the V-gain by measuring Vi and Vo as shown.

Unbalanced-out: V gain = Vo/Vi
Balanced-out: V gain = (Vo/Vi) x 2

It does not matter of unbalance-in or balanced-in.



:darkside:
 

Attachments

  • jboz measurement.jpg
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#230
At least... it works.
Thx for this very nice sketch.

All this details about testing procedure, (even where placing probes, where not, etc).. are very usefull for people like me,
since I never managed to use properly my recently ebayed scope...
It will encourage me to give other try


Manu
 
#233
I couldn't figure out how my little gain-stage could put out so little voltage. It just didn't make sense. So, I connected my VOM to my gain-stage. I set the VOM reading to AC since the gain-stage was receiving a 1000hz signal:

input: 0.375v

output: 7.8v

My scope reads increments differently than I thought; each little mark means a division, not just the large grid lines. It doesn't even seem to matter that the probe is 10x, it still matches the VOM. A bit confusing......

My gain is high: 20.8

BTW, the gain-stage begins to clip when I ask it to deliver more than 7.8 volts.

Does it seem that I'm on the correct path, or have I deluded myself? 😀

Wouldn't be the first time.......

Edit: I connected my VOM just like the last pic I submitted, using Babowana's drawing.
 
#234
carpenter said:
It makes a huge difference, with my system, where I place the input probes. The input voltage is double when I probe the + and - inputs together verses + and ground.
Click to expand...


We are going to check V-gain.
It doesn't matter whether we use balanced or unbalanced input.
The unbalanced output devided by the input (balanced or
unbalanced) gives us the v-gain.

Hope you will check also at lower frequencies . . .



:darkside:
 
#236
carpenter said:
As per my last post, does my measuring process seem correct
with the volt/ohm meter?
Click to expand...


I guess your scope has eight divisions vertically.
Just adjust for both channels to have the same volts/div setting.
And, trust the results coming from the equipment.
For example, If the volts/div setting is 5 volts,
then each of the eight vertical divisions represents 5 volts.

Meanwhile, if you use different v/d settings between two channels,
then put out your HP calculator to practice math with
the different scaling factors.

Oh . . . I’m assuming that you set the both probes to 10X.
Otherwise, you need another practice of the math with
the different scaling factors.


:darkside:
 
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