what type of High frequency?

[Miracletech]

Ok, Would aa pocket scope do the job?

 

[Nigel Goodwin]

A real full size scope will generally be MUCH better.

 

[Miracletech]

The $$ Matters though, So, We Gotta invest rightfully...

 

[AnalogKid]

Excuse me Forum, But what type of a frequency would make the voltage on the Base Emitter junction of a BJT 0.22Volts?

23 posts. No schematic. No answer.

ak

 

[Nigel Goodwin]

23 posts. No schematic. No answer.

There can be no answer - as the question makes no sense at all - and his entire premise is wrong in the first place.

 

[AnalogKid]

Actually, I understand his question. But without a schematic , there is no specific answer.

ak

 

[Nigel Goodwin]

Actually, I understand his question. But without a schematic , there is no specific answer.

Perhaps you'd care to explain it then?.

 

[unclejed613]

I am testing if the base emitter diode voltage (VBE) decreases with Higher frequency.

it shouldn't... however Vbe (in silicon) has a negative temperature coefficient of -2.2mV/DegC. transistors lose gain as frequency rises due to capacitances between the junctions, but that doesn't change Vbe.

 

[ChrisP58]

Isn't having all in one Better?

Sometimes. But mostly not.

The fact that they are the same device limits their effectiveness when you need both. I frequently need to look at both a waveform and a voltage at the same time. With an integrated instrument, you need to shift back and forth from one mode to the other.

The times I have used my integrated scope/meter are when I go out into the field to work and I'm limited in what I can carry with me.

 

[Miracletech]

Perhaps you'd care to explain it then?.

The reason why I ask a question on a forum is not for "Schematic Purposes". I asked about a "High frequency on a bjt" and said I am designing a boost converter, So, What's wrong?

 

[Miracletech]

Do I need a Schematic for a Boost smps? 75% of the electronics world Kind of knows that. I ask questions short and sharp, Schematics or not.

 

[atferrari]

Weather here is improving; this thread not at all. Enough of it.

 

[Nigel Goodwin]

The reason why I ask a question on a forum is not for "Schematic Purposes". I asked about a "High frequency on a bjt" and said I am designing a boost converter, So, What's wrong?

The question wasn't to you, it was to AnalogKid who claimed to understand what you were asking - but he's not responded. But your question was meaningless, and a schematic is ALWAYS very important - there are numerous different types of boost SMPS's - and posting the exact schematic would enable people to have a chance of giving meaningful replies to questions that make no sense.

 

[Miracletech]

I'm Done.

 

[Boxnut]

Presuming a DC-DC boost converter, this is a PWM output so there will be small changes in bias. doesn't sound unusual, and the cold running just shows the load is very low. Consider the dutycycle here is quite low. You will see this when you can look at it with a scope.

 

[Miracletech]

Ok. Thank you very much.

 

[gophert]

A Swiss Army Knife is usually a pretty poor knife. The tooth pick, file and scissors don't work very well either. The spoon is ok but the milk from my cereal gets into the hinge every scoop. The hinge is hard to clean. Dedicated tools are usually much better than multitools.

 

[Miracletech]

Okie dokie. That's a good advice for a beginner.