2.  Signal flow graphs are an alternative to block
diagrams.
 Unlike block diagrams which consist of blocks,
signals , summing junction and pickoff points a
signal flow graph consist only of branches and
nodes .
 Branches represent systems.(i.e. G(s) )
 Nodes represent signals . (it can be any signal i.e.
C(s),V(s)……etc.

3.  A system in a signal flow diagram is represented by a
line with an arrow showing the direction of signal
flow through the system.
 Adjacent to line we write transfer function.
 A signal is a node with the signals name written
adjacent to the node.
 Each signal is sum of signals flowing to it.
 In summing negative signals we associate negative
sign with the system not with a summing.
 In each case we will first convert the signals to nodes
and then interconnect the nodes with system
branches.

4. 1. System:
3. Interconnection of system
and signal
2. Signal:
Here each signal is sum of signals
flowing into it. So
V(s)=R1(s)G1(s)-R2(s)G2(s) +
R3(s)G3(s).
C1(s)= V(s)G4(s)=R1(s)G1(s)G4(s)-
R2(s)G2(s)G4(s)+R3(s)G3(s)G4(s)
C2(s)=V(s)G5(s)=R1(s)G1(s)G5(s)-
R2(s)G2(s)G5(s)+R3(s)G3(s)G5(s)
C3(s)=-R1(s)G1(s)G6(s)+R2(s)G2(s)
G6(s)-R3(s)G3(s)G6(s)
G(s)
V(s)
C1(s)
C2(s)
C3(s)
R1(s)
R2(s)
R3(s)
G1(s)
G3(s)
G4(s)
-G6(s)
-G2(s) G5(s)
V(s)

5. C(s)
Cascaded form
Parallel form
Feedback form
Conversion into signal flow
graphs:
Different forms of Block
Diagrams: