555 Timer Ramp Generator

The post explains how a IC 555 timer ramp generator circuit can be made using a single IC 555 and few other passive components

When a capacitor gets charged from the source of voltage via resistor, the capacitor generates high waveform. The charging of the capacitor from a fixed source of current also generates ramp. This project is based on the said foundation. Following is a circuit diagram of ramp circuit generator using 555 timer. In this diagram, the resistor in the circuit is alternated with a PNP transistor. Using PNP enables producing constant current charge.

555 ramp generator circuit


The current charge with the help of PNP is signified as:
ic = VCC – VE / RE
where VE = R2 / (R1 + R2) *VCC + VBE

When a trigger starts the monostable multivbrator as shown in figure, the PNP current source forces a constant charging into the capacitor C. The voltage across the capacitor is, therefore, a ramp as illustrated in the figure. The slope of the ramp is given as

When 555 monostable multi-vibrator timer is enabled, the source of current from the PNP pushes to charge constantly to C Capacitor. Therefore, the voltage available in the capacitor is a ramp [as shown in Fig 1.0].

Slope, s = I/C

The following image shows the waveform of the slope of the IC 555 ramp generator circuit

ramp trigger and waveform