ASTABLE OPERATION

When the circuit is connected as shown in figure 4

it triggers itself and free runs as a multivibrator. The

may be precisely set by the ratio of these two

resistors.

In the astable mode of operation, C charges and

triggered mode, the charge and discharge times

and therefore frequency, are independent of the

supply voltage.

Figure 5 shows actual waveforms generated in this

mode of operation.

The charge time (output HIGH) is given by :

and the discharge time (output LOW) by :

Thus the total period T is given by :

The frequency of oscillation is then :

f

=

1

T

=

1.44

The duty cycle is given by : D

=

Reset

Out

R

C

R

A

B

Control

Voltage

0.01 F

µ

1/2

TS556

Figure 4

Ω

Ω

µ

t = 0.5 ms / div

OUTPUT VOLTAGE = 5.0V/div

CAPACITOR VOLTAGE = 1.0V/div

L

R = R = 4.8 k , C = 0.1 F , R = 1.0k

AB

Figure 5

TS556C,I,M

9/11