10 V
100 k
Ω
V
OUT
150 k
Ω
50V
X
+
_
1 k
Ω
2.2 k
Ω
+
_
V
X
+
_
R
IN
I
IN
V
IN
R
F
A
Lesson 15 – Dependent Sources #3 (Section 42) (CLO 41)
This lesson looks at input and output resistance of a dependent source circuit.
A very important concept involves the
effect of feedback on
R
IN
and
R
OUT
.
If there is no feedback resistor, the input
resistance is simply
=
=
IN
IN
IN
R
I
V
/
250 k
Ω
.
However, if we add
R
F
to the
circuit,
R
IN
changes.
k
V
I
100
10
X
IN

=
But last lesson we found that
F
X
3060
1
6
R
k
V
+
=
So that
F
F
N
IN
IN
3060
1
6
10
1000
100
3060
1
6
10
10
R
k
k
k
R
k
I
V
R
I
+

=
+

=
=
Again, we can build a table that relates
R
IN
to
R
F
.
The input resistance changes by 2.5 times depending on
R
F
.
There are two points to be made: First, the input resistance varies
with feedback and second, the designer has control of the input
resistance to some extent.
The last concept involves finding a Thévenin Equivalent circuit as seen by the 2.2 k
Ω
load.
Without elaboration we would get
F
X
T
OC
3060
1
300
50
R
k
V
V
V
+

=

=
=
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 MAURICIODEOLIVERIA
 Input/output, Holden VT Commodore, lookback method

Click to edit the document details