555 VCO discharges timing cap C1 completely to the negative rail via a Reset pulse

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Other Materials from the Main Document

• Article «Can a free running LMC555 VCO discharge its timing cap to zero?»
• Figure 1. 555 VCO discharges timing cap C1 completely to the negative rail via a Reset pulse
• Figure 2. The VCO waveforms; reset pulses at the end of each timing cycle, and is triggered when V_C1 = V_CON, to force an adequately complete discharge of C1
• Figure 3. Log plot of the frequency versus control voltage for the two-octave linear-in-pitch VCO. [X axis = V_CON volts (inverted), Y axis = Hz / 16 = 250 Hz to 1 kHz]
• Figure 4. R4 sums ~6% of V_CON with the C1 timing ramp to get the improvement in linearity shown in Figure 5
• Figure 5. The effect of the R4 modification showing a linearity improvement. [X axis = V_CON volts (inverted), Y axis = Hz/16]