COMPUTING

Chapter 7Pulse Circuits and Waveform GeneratorsThis chapter is an introduction to several pulsed circuits and waveform generators also knownas relaxation oscillators. These circuits are part of a family of circuits that include differentiators,integrators, clipping and clamping circuits, pulse−timing and delay circuits, logic circuits,and switching circuits. In this chapter we discuss the three types of multivibrators, the 555Timer, and the Schmitt trigger. Sinusoidal oscillators are discussed in Chapter 10.7.1 Astable (Free−Running) MultivibratorsAn astable or free−running multivibrator, shown in Figure 7.1, is essentially a digital clock which hastwo momentarily stable states which alternate continuously thus producing square pulses as shownin Figure 7.2. We have assumed that all devices in the circuit of Figure 7.1 are identical.V CCR CR B R BR COutput 1 Output 2CQ 1 Q 2CFigure 7.1. Astable multivibratorOutput 1Output 2Figure 7.2. Output waveforms of the astable multivibratorLet us now consider Output 1 and assume that the time ON T 1 and time OFF T 2 are equal andthe period is T as shown in Figure 7.3.Electronic Devices and Amplifier Circuits with MATLAB Computing, Second EditionCopyright © Orchard Publications7−1