Launchpad
P1.1 attached to touch screen top
P1.2 attached to touch screen right
But…
P1.1 and P1.2 attached to J3
Multivibrators and wave shaping
circuits
Multivibrators
• Bistable
• Monostable (one shot)
• Astable
C1
V in
R1 1k
3
+
+
6
V out
-
R2 1k
4
2
7
R3 1k
Vcc
Monostable multivibrator
Comparator
Schmitt Trigger (voltage output)
Figure 13.19 (a) The bistable circuit of Fig. 13.17 with the negative input terminal of the op amp disconnected from ground and connected to an
input signal vI. (b) The transfer characteristic of the circuit in (a) for increasing vI. (c) The transfer characteristic for decreasing vI. (d) The complete
transfer characteristics.
Relaxation Oscillator, astable multivibrator
Figure 13.24 (a) Connecting a bistable multivibrator with inverting transfer characteristics in a feedback loop with an RC circuit results in a squarewave generator.
Relaxation Oscillator
Figure 13.24 (Continued) (b) The circuit obtained when the bistable multivibrator is
implemented with the circuit of Fig. 13.19(a). (c) Waveforms at various nodes of the
circuit in (b). This circuit is called an astable multivibrator.
Output Limiting
Figure 13.23 Limiter circuits are used to obtain more precise output levels for the bistable circuit. In both circuits the value of R should be
chosen to yield the current required for the proper operation of the zener diodes. (a) For this circuit L+ = VZ1 + VD and L– = –(VZ2 + VD), where VD is
the forward diode drop. (b) For this circuit L+ = VZ + VD1 + VD2 and L– = –(VZ + VD3 + VD4).
vthreshold  5
100
 0.49V
100  10, 000
555 Timer
Figure 13.27 A block diagram representation of the
internal circuit of the 555 integrated-circuit timer.
Astable
Figure 13.29 (a) The 555 timer connected to implement an astable multivibrator. (b) Waveforms of the circuit in (a).
Monostable
Vcontrol , varies width
Figure 13.28 (a) The 555 timer connected to implement a monostable multivibrator. (b) Waveforms of the circuit in (a).
Variable voltage
Figure 13.31 (a) A three-segment sine-wave
shaper. (b) The input triangular waveform and
the output approximately sinusoidal waveform.