1.RC charging circuit
The power supply charges the capacitor through a resistor. At first, the voltage at both ends of the capacitor is 0, so the voltage of the voltage is on the resistor. At this time, the current is large and the charging speed is fast. As the voltage across the capacitor rises, the voltage across the resistor drops, so does the current and the charging speed.
The speed of charging is related to the size of resistance and capacitance. The larger the resistance R, the slower the charging, and the larger the capacitance C, the slower the charging. Constant t(tao)=RC to measure the charging speed.
2.RC discharge circuit
Capacitor C discharges through resistor R. Because the voltage at the beginning of capacitor discharge is E, the discharge current I=E/R, and the changing current is very large, the discharge speed is very fast. With the continuous discharge of the capacitor, the voltage of the capacitor also drops. The current also decreases rapidly.
The discharge speed of capacitor is related to RC, and the larger the resistance of R, the slower the discharge speed. The larger the capacitance, the slower the discharge speed.
3.RC integrating circuit
RC integration circuit can convert rectangular wave into triangular wave (or sawtooth wave).
Circuit working principle:
At 0-t 1, the rectangular wave is at a low level, and there is no voltage to charge the capacitor, so the output voltage is 0.
At t 1-t2, the rectangular wave is at a high level, the capacitor is charged with voltage, and the output voltage rises slowly. Because the time constant tao=RC is much larger than the pulse width tw, the output voltage cannot reach the high level Vm at time t2.
At t2-t4, the rectangular wave is at a low level, and the capacitor C begins to discharge.
The integrating circuit should satisfy that the time constant tao=RC is much larger than the pulse width tw, usually larger than 3tw.
4.RC difference channel
RC difference channel can convert rectangular wave into narrow-width spike pulse signal.
Circuit working principle:
During 0-t 1, the rectangular wave is at a low level, the input voltage is 0, and no current flows through the capacitor and resistor, so the voltage across the resistor is 0.
During t 1-t2, the rectangular wave is at high level and the input voltage is Vm. At this time, the capacitor has not been charged, so the voltage across the resistor is Vm. After t 1, the capacitor begins to charge, and the voltage across the resistor also drops. Because the time constant is very small, the capacitor charges quickly, the capacitor voltage rises to Vm, and the resistance voltage is 0.
At t2-t3, the rectangular wave is at a low level, the input voltage is 0, the capacitor is equivalent to a power supply, and the resistor gets a positive voltage at the bottom and a negative voltage at the top. With the discharge of the capacitor, the voltage across the resistor also drops.