RC Charge/Discharge
CI
CircuitSim
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Created Apr 19, 2026
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Updated Jun 30, 2026
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About this circuit
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Circuit notes
RC Charge / Discharge
The Circuit
This circuit demonstrates a capacitor charging and discharging in response to a DC voltage pulse.
Simulation
- A transient simulation is run for 20 mS with a 100 uS step size.
- The voltage Vin is measured between the voltage source V1 and ground.
- The voltage Vcap is measured between the positive side of the capacitor C1 and ground.
- The current Ir is measured through the resistor R1.
Notes
Use the RC Time Constant to calculate the capacitor charge / discharge time.
The time to charge the capacitor to ~63.2% is:
Where R is the resistance of R1 and C is the capacitance of C1.
In this circuit the first 5V pulse starts at time = 0mS. Therefore we expect the capacitor to charge to:
by time =
Use the table to check.
Components used
No component metadata available.
SPICE netlist
* **************************************************
* Generated from CircuitSim Schematic
**************************************************
C_C1 VP2 0 1u
R_R1 N2 N1 1K
X_U1 VP1 0 CLOCK DUTY=50 VHIGH=5 VLOW=0 PERIOD=1m
V_VP1 VP1 N1 0
V_IP1 VP2 N2 0
**************************************************
* Models and supporting definitions follow
**************************************************
* Clock generator with duty cycle in percent (0–100)
.subckt CLOCK OUT GND VHIGH=5 VLOW=0 PERIOD=1m DUTY=50
.param DUTY_FRAC = { DUTY / 100 } * Convert percent to fraction
.param TON = { PERIOD * DUTY_FRAC }
VCLK OUT 0 PULSE( VLOW VHIGH 0 1n 1n {TON} {PERIOD} )
.ends CLOCK
**************************************************
* Simulation settings
**************************************************
.tran 0.00009999999999999999 0.02 0
.save V(VP1) V(VP2) I(V_IP1)
.endTry this circuit yourself
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