Some notes on the
curves:
1.
DC biasing point - when there is no signal of
interest, this is the amount the current through BJT ,
and Vo2 is the voltage at Vout. Choice of Vo2 is by design - affected by Vdd
available, amount of signal gain required, quiescent power dissipation by BJT,
linearity required...
2.
Base current deviate from DC biasing point
following the signal of interest
3.
Base current changes will cause collector
current to change according to curves shown as Ib1, Ib2, Ib3...,
the current will cause voltage changes on Vout, choice of Rc will affect the
magnitude of the Vout signal.
4.
Non-linear region of IV curve (Cut-Off region) -
if Vout swing were to reach this area, the amplification of signal will be
distorted. This will cause clipping on output signals, THD (3rd
order harmonic distortion)…
Additional note about
BJT:
1.
BJT is actually Current Controlled Current Source
- Base current controls Collector (compare this to Mosfet - Voltage Controlled
Current Source – Gate to Source voltage controls Drain current)
2.
Rc will determine the
signal gain, DC biasing point and some other parameters.
3.
From Kirchhoff law (V, I)
a.
only interception of each Ib curve with the load
line is possible for a given circuit
b.
so as Ib changes, the instantaneous Vc (collector voltage) will be the
intersections of load line with that instantaneous Ib curve.
Nice blog… Thanks for sharing very useful information about electrical circuits.
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