Brief charging Capacitor Voltage Ramp Circuit using LM334 Current Source

Simple charging capacitor voltage ramp using constant current source schematic diagram by electronzap electronzapdotcom
Simple charging capacitor voltage ramp using constant current source schematic diagram by electronzap electronzapdotcom

A steady amount of current from a current source being used to charge a capacitor, results in a steady rise of voltage. A steady voltage change is called a ramp.

  • Pushbutton (or other switch) parallel to the capacitor can instantly discharge the capacitor when the switch is closed. Opening the switch allows the capacitor to start charging based on the current set by the LM334. Only use an approx. 1,000µF or less capacitor to prevent a destructive amount of current.
  • LM334 is a 3 terminal component that looks like a transistor in the TO-92 package. It passes a certain amount of current based on resistance between pins R and V-. That is true for as long as there is enough supply voltage across it to do so. Always consult the datasheet for the most accurate specifications and limitations.
    1. 0.064V (64mV) divided by set resistor (resistor between R and V-) sets the current. 0.064V/64Ω = 0.001A (1mA) of current.
      • 0.001F (1,000µF capacitor gains 1 volt per second while it is charged with 0.001A (1mA) of current.
    2. Rated for 1µA (0.064V/0.000001A = 64,000Ω) to 10mA (0.064V/0.01A  = 6.4Ω).

Video:

Discharging ramp:

Simple discharging capacitor voltage ramp circuit schematic by electronzap electronzapdotcom
Simple discharging capacitor voltage ramp circuit schematic by electronzap electronzapdotcom

Discharging a capacitor with a current source results in a discharging ramp voltage.

The current source is placed parallel to a capacitor.

Closing a series switch instantly charges the capacitor.

Once the switch is opened, current will stop coming from the switch, and will be provided by the capacitor as it discharges through the current source.

Video:

Brief Circuit Schematics with Short Video List of Pages

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