Amplifiers reaction
1) Amplifier of tension:
It must give in escape a tension proporziona them to the income tension and us it succeeds as well as better the how much the more resistance of income is high and the resistance of escape is low, to such aim a tension is captured in parallel from the escape lowering the Ror while in income tension in series comes inserted one increasing Ri .
2) Amplifier of current:
Current must give in escape one proporziona them to the income current and the how much the more resistance of income succeeds us as well as better is low and the resistance of escape is high, to such aim one is captured in series current from the escape increasing the Ror while in income current in parallel comes inserted one lowering Ri .
3) Amplifier of transconduttanza:
Current must give in escape one proporziona them to the income tension and it succeeds to us better as well as how much the more are high is the resistance of income that the resistance of escape, to such aim captures in series one current from the escape increasing the Ror while in income tension in series comes inserted one increasing Ri .
4) Amplifier of transresistenza:
It must give in escape a tension proporziona them to the income current and it succeeds to us better as well as how much the more are low is the resistance of income that the resistance of escape, to such aim captures in parallel a tension from the escape lowering the Ror while in income current in parallel comes inserted one lowering Ri .
5) Amplification of a reazionato amplifier:
is had from which collecting X0 are reached the expression of the
reazionata amplification 
which is valid
under the following hypotheses:
to) the block To it is unidirezionale (Y21A > > Y12A)
b) the block b is unidirezionale (Y12B > > Y21B)
c) the two interconnected nets To and b behave like nets 2-doors
It is observed that if |Tob| >> 1, the characteristics of the reazionato amplifier depend solo from the feedback net b that it can be realized with elements passes to you having elevated characteristic of precision and stability.
6) ring Gain:
7) Factor of desinsibilizzazione of the system:
a lot important is a factor and often comes given in
logaritmica shape 
, if N is negative the feedback
is negative otherwise is positive.
8) Considerations on the used negative feedback for desensibilizzare the amplifier from the variations of the gain to open chain:
to) Deriving 
respect to To, the term To f is still characterized in the
derivative , carrying it to the
denominator of 1° the member 
is had and being
normally bA>>1 it obtains
that the reazionata amplification is desensibilizzata regarding the
variations of the gain to chain opened To Derivando instead Tof regarding b is reached 
from which evince that the
variations in the net of reaction b ripercuotono on the reazionata amplification therefore b net will have to be one a lot
stable.
b) If they are had of the amplifiers to put in cascade convene to controreazionare the cascade rather than to controreazionare the single amplifier, the result is deduced confronting the sensibility to the variations of To in the two cases.
9) Effect of a sampling or a comparison of type parallel:
It lowers the resistance of income of the amplifier if draft of a comparison while it lowers the resistance of escape if draft of a sampling.
10) Effect of a sampling or a comparison of type series:
It raises the resistance of income of the amplifier if draft of a comparison while it raises the resistance of escape if draft of a sampling, mnemonically enough to remember that âSerieâ? and âSuâ? they begin both with the letter âSâ?.
11) immediate Criterion in order to understand if a reaction net is in series or parallel:
Affinche is in parallel must be common is to the income that to the escape, if therefore it is not then is in series.
12) Criterion of analysis of a retroazionato amplifier:
It is necessary to characterize the outline of the correspondent retroazionato circuit not holding account of the following considerations:
to) the net to place in income currency cortocircuitando the escape if the withdrawal of money is carried out in parallel or opening the escape in the case that the withdrawal of money is carried out in series
b) the net to place in escape currency cortocircuitando the income if the comparison is carried out in parallel or opening the income in the case that the comparison is carried out in series.
c) if tension marks them retroazionato is one to use a generator of Thevenin otherwise a generator of Norton
d) to replace the active device
with its equivalent circuit and to estimate 
and
To from which pu² gaining 
and through it Tof , Rif and R0f .
13) Analysis of a transresistenza amplifier:
Having draft of a common emettitore a resistance of R' feedback connected between the collector and the base, as escape largeness considers tension V0 while as income largeness the currentthe S distributed from the generator of marks them. The analysis is carried out in the following steps:
to) 
in how
much is estimated being a common emettitore has V0 > > VB .
b) the circuit of the amplifier not
retroazionato is designed but loaded from the feedback net, in
particular since in escape a tension in parallel is captured, in order
to cancel of the effect it comes cortocircuitata like also inasmuch as
in income immette one current in parallel, in order to cancel of the
effect the income comes cortocircuitato. From the net that turns
out some it deduces 
, 
, 
and the transresistenza not
retroazionata 
.
c) you notice b and RM can
be calculated the factor of desensitization 
from which the retroazionate largenesses 
,
, are obtained 
.
The calculations carry out to you however are valid single
if the current 
that slides between the income
and the escape through the feedback net is infinitesimal regarding the
current 
due to the net of amplification To,
replacing are had that this condition is respected if 
.
14) Analysis of a current amplifier:
It is constituted from two common emettitore places in cascade, the escape currentthe 0 is approximately equal to the currentand that it comes captured in series through a R resistanceand and brought back in parallel in income through the R' resistance connected between the collector of according to transistor and the base of the first one, for comfort of analysis the generator of tension with a current generator is replaced and it is proceeded in the following steps:
to) 
in how
much 
is estimated.
b) the circuit of the amplifier not
retroazionato is designed but loaded from the feedback net in
particular since in escape one is captured current in series in order
to cancel some the effect the escape like also is opened inasmuch as
in income immette one current in parallel in order to cancel of the
effect the income comes cortocircuitato. From the net that turns
out some it deduces 
, 
, 
and 
where the added
terms of correction are not other that partitori of current.
c) you notice b and To the factor
of desensitization can 
be calculated and
through it the retroazionate largenesses , and 
.
The calculations carry out to you however have single validity ifthe f >>the 0 .