开云体育A BJT is inherently a current-controlled and -controlling device.
Ibe controls Ice, within the limits of the surrounding circuitry.
I have no idea why you don't want to use current sources if you
are after a device behaviour model. If there is another goal, it
would be a good idea to tell us, otherwise we can lead you to a
perfect but perfectly useless circuit. To get the device in your earlier schematic into active mode, you'll have to drive the base with less current than I(e)/Hfe. This is known as "biasing a transistor" and is pretty standard electronic design. Most good biasing schemes that I know of use some form of current sources, since Vbe varies with temperature so much. Do a bit of net search for "transistor bias" and related terms; you should be able to come up with something useful. In your original schematic (I'm not going to bother downloading
another), note that V1 is 5V and V2 is -1V. The base current of Q1
will therefore be somewhere around ((5V) - (0.6V) - (-1V))/(100ohm
+ 1kohm) = 4.9mA. If Q1 has an Hfe of about 100 (just a WAG,
understand), then Q1 will be capable of carrying? 490mA through R3
-- that WON'T happen given R3's value and the 5V from V1. To be in
active region, Q1's base current has to be less than 0.01 *
whatever current V1 can provide through R2 + R3. If you _really_ want to use V2 and R1 to bias Q1, you'll have to
increase V1 to a positive value near V1 - V(b,e): so somewhere
around 4.0V to 4.5V. A base-emitter shunt resistor might also be
helpful, but that will be left as an exercise for the student. Donald. On 4/4/25 08:09, john23 via groups.io
wrote:
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