Elenco Electronics EP-130 - Pulse Frequency Multiplier

-
121
-
This is a pulse frequency multiplier with on
e
transistor. It doubles the frequency of the input si
g
nal
,
so it is also called a pulse frequency doubler.
The operational amplifier IC acts as a square-wav
e
oscillator. The output from the oscillator is an A
C
si
g
nal of about 500Hz
.
When you
f
inish the wirin
g
, set the switch to position
A to turn on the
p
ower. Connect the ear
p
hone t
o
term
i
na
l
s 93 an
d
134 an
d
press t
h
e
k
ey to
li
sten to
the oscillatin
g
sound o
f
500Hz. Note the pitch o
f
th
e
t
one.
Now, connect the ear
p
hone to terminals 13 and 14
a
nd press the key. Listen throu
g
h the earphone; thi
s
time you hear a sound that is an octave hi
g
her than
the previous sound. This means the
f
requency i
s
doubled to 1,000Hz
.
How does this work? The operational ampli
f
ier is
configured as an oscillator. Transistor Q1 receives
a
signal
f
rom the operational ampli
f
ier through th
e
transistor’s base; the base volta
g
e chan
g
es with the
osc
ill
at
i
ons.
Thi
s resu
l
t
i
s t
h
at oppos
i
te p
h
ase s
i
gna
ls
a
ppear at the transistor’s collector and emitter - when
one s
i
gna
l
i
s at a wave max
i
mum, t
h
e ot
h
er
i
s at t
he
wave minimum. The two outputs from transistor
Q1
a
re a
ppli
e
d
to
di
o
d
es
D
a an
d
Db
.
Th
e
di
o
d
es
p
as
s
through only the positive portion o
f
the waves, s
o
t
h
ese two s
ig
na
l
s com
bi
ne to
g
et
h
er to pro
d
uce
a
doubled
f
requency.
No
t
es
:
EXPERIMENT #101: PULSE FREQUENCY MULTIPLIE
R
Wiring
S
equence
:

12
5
-127-
9
1-1
3
-EARPH
O
N
E

134-110-92-80-83-76-14-EARPH
O
N
E

32-63-87-13
1

33
-47-1
07

35
-4
8
-1
05

89
-
36
-7
0
-
121

88
-
90
-1
03
-4
6

8
1-
86
-
6
7-1
37

85
-
68
-1
09

6
9-82-8
4

7
5
-7
7

7
8
-1
06
-12
8

7
9
-
108
-
126

94-104-13
8

11
9
-124-1
35

122-1
32
Schemati
c