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CACD Group updated 2000.03.30 Author Janez Puhan |
Sawtooth Waveform GeneratorThe circuitThe following circuit belongs to the family of relaxation oscillators. Complementary bipolar transistors establish a DC characteristic similar to that of a gaseous discharge tube. At the beginning of the cycle, both transistors are in the non-conducting state. C1 is charged via R5 with an exponentially increasing voltage. When the firing voltage is reached, a regenerative process starts by which the capacitor is discharged until the current drops below a holding threshold. Thereafter, a new operating cycle begins. The input file (sawtooth_waveform_generator.cir)sawtooth waveform generator * fo = 1 / (c1 r5 ln(1 + r2 / r1)) .control tran 5us 1ms uic plot v(2) xlabel t[s] ylabel output[V] title 'TRAN analysis' plot v(5) xlabel t[s] ylabel v(5)[V] title 'TRAN analysis' .endc v0 1 0 dc 15V r1 1 3 1.5k r2 3 0 3.3k r3 4 0 39k r4 5 0 100 r5 1 2 100k c1 2 0 2.2nF ic=0 q1 4 3 2 noname1 q2 3 4 5 noname2 .model noname1 pnp cjc=10pF rb=100 is=1p .model noname2 npn cjc=10pF rb=100 is=1p .end The results |
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