Ramp generator

  
The linear charging ramp is most useful where linear control of voltage is required. Some possible applications are a long period voltage controlled timer, a voltage to pulse width converter, or a linear pulse width modulator. Ql is the current source transistor, supplying constant current to the timing capacitor Ct. When the timer is triggered, the clamp on Ct is removed and Ct charges linearly toward Vcc by virtue of the constant current supplied by Ql. The threshold at pin 6 is ¥3 Vcc; here, it is termed Vc.
Ramp generator  - schematic

When the voltage across Ct reaches Vc volts, the timing cycle ends. The timing expression for output pulse with is:




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