multivibrator

download report

Transcript multivibrator

MULTIVIBRATOR
Individual Sequential Logic circuits can be used to build more
complex circuits such as Multivibrators, Counters, Shift Registers,
Latches and Memories etc, but for these types of circuits to operate
in a "sequential" way, they require the addition of a clock pulse or
timing signal to cause them to change their state.
Clock pulses are generally continuous square or rectangular shaped
waveform that is produced by a single pulse generator circuit such
as a Multivibrator
MULTIVIBRATOR
Sequential logic circuits that use the clock signal for synchronization are
dependen upon the frequency and clock pulse width to activate there
switching action. Sequential circuits may also change their state on either
the rising or falling edge, or both of the actual clock signal as we have
seen previously with the basic flip-flop circuits. The following list are
terms associated with a timing pulse or waveform.
Active HIGH - if the state changes occur at the
clock's rising edge or during the clock width
Active LOW - if the state changes occur at the
clock's falling edge
Clock Width - this is the time during which the
value of the clock signal is equal to one.
Clock Period - this is the time between successive
transitions in the same direction, i.e., between two
rising or two falling edges.
Clock Frequency - the clock frequency is the
reciprocal of the clock period, frequency = 1/clock
period
MULTIVIBRATOR
There are basically three types of clock pulse generation circuits:
Astable - A free-running multivibrator that has NO stable states but
switches continuously between two states this action produces a
train of square wave pulses at a fixed frequency.
Monostable - A one-shot multivibrator that has only ONE stable
state and is triggered externally with it returning back to its first
stable state.
Bistable - A flip-flop that has TWO stable states that produces a
single pulse either positive or negative in value.
12_ClockMonostb555.lvw
12_MultiV.lvw
http://www.electronics-tutorials.ws/sequential/seq_3.html
MULTIVIBRATOR
Clock - Detak
In electronics and especially synchronous digital circuits, a clock signal is a
particular type of signal that oscillates between a high and a low state and is
utilized like a metronome to coordinate actions of circuits. (sinyal berbentuk
pulsa)
A crystal oscillator is an electronic oscillator circuit that
uses the mechanical resonance of a vibrating crystal of
piezoelectric material to create an electrical signal with a
very precise frequency to provide a stable clock signal for
digital integrated circuits.
MULTIVIBRATOR
Clock - Detak
Pin
Name
Purpose
1
GND
Ground, low level (0 V)
2
TRIG
OUT rises, and interval starts, when this input falls below 1/2 of CTRL voltage.
3
OUT
This output is driven to approximately 1.7V below +VCC or GND.
4
RESET
A timing interval may be reset by driving this input to GND, but the timing does not begin again until
RESET rises above approximately 0.7 volts. Overrides TRIG which overrides THR.
5
CTRL
"Control" access to the internal voltage divider (by default, 2/3 VCC).
6
THR
The interval ends when the voltage at THR is greater than at CTRL.
7
DIS
Open collector output; may discharge a capacitor between intervals. In phase with output.
8
VCC
Positive supply voltage is usually between 3 and 15 V.
MULTIVIBRATOR
Free Running Multifibrator untuk membangkitkan pulsa digital
M ultifibrator jalan bebas
(free running m ultifibrator)
5V
+5
0
gnd
astabil
4
1K
8
7
470K
6
5V
2
1uF
Pew aktu
(tim m er)
555
+5
3
0
gnd
MULTIVIBRATOR
Switch menggunakan saklar tekan…
Saklar
norm aly off
T ekan = tinggi
K eluaran
5V
L epas = rendah
Perangkat disamping sebagai pembangkit
sinyal digital juga tidak diperkenanka,
karena menyebabkan rangkaian terbuka
pada saat saklar dilepas ( 0 V ≠ gnd )
Solusi
+5
M ultifibrator satu tem bakan
(one shoot m ultifibrator)
5V
m onostabil
0
gnd
Tekanan saklar membangkitkan pulsa
tembakan seperti pada gambar
MULTIVIBRATOR
Bistabil - FF
S
Q
S
R
R
set
reset
set
Q
Mode
operasi
Masukan
S
R
Keluaran
Q
Q
Pengaruh pada
keluaran Q
Larangan
0
0
1
1
Larangan (don’t use)
Set
0
1
1
0
Me-set Q menjadi 1
Reset
1
0
0
1
Me-reset Q menjadi 0
Tetap
1
1
Q
Q
Tgt keadaan sebelumnya
reset