trans2

# trans2 - ELEC 101 18 Transient Circuits 25 Bistable Circuit...

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Unformatted text preview: ELEC 101 18 Transient Circuits 25 Bistable Circuit 2009/10 Spring Schmitt trigger R1 Bistable circuit has two stable states. R2 A positive-feedback loop can generate a bistable circuit. R1 V VI R2 V +Vsupply V VO V VO Vsupply +Vsupply VO VTL VTH 0 VO stables at positive and negative supply voltages +Vsupply and Vsupply. R1 Vsup ply R1 R 2 which enforce VO to +Vsupply. When VO = +Vsupply , V Note: With positive feedback V V . VI Vsupply Since V VTL R1 VO R1 R 2 R1 Vsup ply R1 R 2 and VTH R1 Vsup ply R1 R 2 ELEC 101 Transient Circuits 26 Bistable Circuit with Noninverting 2009/10 Spring As a Hysteretic Comparator Transfer Characteristics R1 R1 R2 R2 VI VI VO V VR VO VO VO Hysteresis +Vsupply +Vsupply VTL VTH 0 VI Vsupply Since V VTL R2 R1 VI VO R1 R 2 R1 R 2 R1 Vsup ply R2 and VTH R1 Vsup ply R2 0 VI Vsupply ELEC 101 19 Transient Circuits 27 Square Waveform Generator Generate a square waveform with frequency controlled by R1, R2, R and C. R1 VO T +Vsupply 0 R2 V 2009/10 Spring time Vsupply VO V to +Vsupply V +Vsupply C R If RC time constant is much larger than the period T, a triangular waveform can be obtained at V. 0 time Vsupply to Vsupply V+ +Vsupply 0 time Vsupply R1 R1 R 2 ...
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