NE556 - SA556 - SE556
Figure 14. Tone burst generator
Application information
+15V
Reset
14
Vcc
14
4
RA
R t
Trigger
10
5
Discharge
6
13
Trigger
Output
Reset
RB
1/2
NE556
SE556
1/2
NE556
SE556
Discharge
12
Threshold
1
2
8
Trigger
Output
Control
Control
11
3
9
Threshold
Ground
C2
C1
m
0.01 F
Ground
m
F
0.01
Ground
T = 1.1 R t .C1
1.44
f =
RA + 2RB ) C
For a tone burst generator the first timer is used as a monostable and determines the tone
duration when triggered by a positive pulse at pin 6. The second timer is enabled by the high
output or the monostable. It is connected as an astable and determines the frequency of the
tone.
Figure 15. Monostable operation
VCC
RL
RA
4
14
(10)
(8)
Trigger
1
2
(13)
6
1/2
NE556
SE556
(12)
Output
(9)
5
(11)
7
3
C
RL
10nF
T = 1.1 RA .C
9/16
STMICROELECTRONICS [ ST ]
