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555 Bootstrap Sawtooth wave Generator Circuit

2015-01-30 16:03  
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555 Bootstrap Sawtooth wave Generator Circuit
555 Bootstrap Sawtooth wave Generator Circuit
As shown in the figure 5-4, the 555, R2, R3 and C1 constitute a Bi-stable multi-vibrator,the frequency of the Bi-stable multi-vibrator f=1.44/ (R1+R2+2R3)C1 and the oscillation frequency is about 665Hz. Much attention should paid on the positive feedback effect of C2, that is, at the same time that emitter follower VT1 outputs sawtooth wave, the positive feedback goes to the upside of R2.Therefore, the pressure drop on R2 remains unchanged, that means the charge rate of C1 remains unchanged, too. Thus, the linearity of the sawtooth wave is greatly guaranteed. Nonlinearity can be limited to below 1% with excellent temperature stability, generally, it is chose under the condition R1C2>10R2C1.