KA555

9

6. Linear Ramp

increases linearly, generating a linear ramp. Figure 13 shows the linear ramp generating circuit and Figure 14 illustrates the

generated linear ramp waveforms.

Ic=(15-10.7)/20k=0.215mA

When the trigger is started in a timer configured as shown in Figure 13, the current flowing to capacitor C1 becomes a constant

current generated by PNP transistor and resistors.

8

4

7

1

2

3

5

6

CONT

GND

Vcc

DISCH

THRES

RESET

TRIG

OUT

+Vcc

R

A

C

R

B

Modulation

Output

Figure 11. Circuit for Pulse Position Modulation

Figure 12. Waveforms of pulse position modulation

Figure 13. Circuit for Linear Ramp

Figure 14. Waveforms of Linear Ramp

1

5

6

7

8

4

2

3

RESET

Vcc

DISCH

THRES

CONT

GND

OUT

TRIG

+Vcc

C2

R1

R2

C1

Q1

Output

I

C

V

CC

V

E

–

R

E

−−−−−−−−−−−−−−−−

=

12

()

Here, V

E is

V

E

V

BE

R

2

R

1

R

2

+

−−−−−−−−−−−−−V

CC

+

=

13

()