Hello,
Using a pn2222 transistor (see attachment), I have done a ramping circuit with a new gain value which is:
2.0 -> 3.3VDC for Vin
and
1.0 -> 0.5VDC for Vout
Most of the transistors I tried resulted in a pretty precise ramp. But other transistors with different betas resulted in imprecise values such as:
2.0 -> 3.3VDC for Vin
and
0.9 -> 0.33VDC for Vout
Since Vc of this circuit is fed back into the base of another transistor which requires an approximate voltage of 0.55 to 0.6VDC to begin its linear region activity, there is too much of an offset for the 0.33VDC value. I will be losing approximately 34% of my linear region because of a premature vout value!!!! That's quite unacceptable.
So what do we do in a case like this.... Do we have to test every transistor and make sure its a certain suitable beta for my circuit.... or perhaps provide different Vs values... for example dip switch #1 makes Vs 1.7VDC, dip switch #2 makes Vs 1.5VDC and so on.....
Also, I never experimented with any transistors other than the pn2222. Is there a transisitor that does exactly what the the PN2222 does, but with a much more precise beta range?
All feedback appreciated!
r
Using a pn2222 transistor (see attachment), I have done a ramping circuit with a new gain value which is:
2.0 -> 3.3VDC for Vin
and
1.0 -> 0.5VDC for Vout
Most of the transistors I tried resulted in a pretty precise ramp. But other transistors with different betas resulted in imprecise values such as:
2.0 -> 3.3VDC for Vin
and
0.9 -> 0.33VDC for Vout
Since Vc of this circuit is fed back into the base of another transistor which requires an approximate voltage of 0.55 to 0.6VDC to begin its linear region activity, there is too much of an offset for the 0.33VDC value. I will be losing approximately 34% of my linear region because of a premature vout value!!!! That's quite unacceptable.
So what do we do in a case like this.... Do we have to test every transistor and make sure its a certain suitable beta for my circuit.... or perhaps provide different Vs values... for example dip switch #1 makes Vs 1.7VDC, dip switch #2 makes Vs 1.5VDC and so on.....
Also, I never experimented with any transistors other than the pn2222. Is there a transisitor that does exactly what the the PN2222 does, but with a much more precise beta range?
All feedback appreciated!
r
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