Capacitive Voltage Divider – Working & Its Applications

What do you observe the moment you see the circuit?
Can you compare the input and output voltages?
Is the voltage being divided at the output?
How does the voltage divide in a series capacitive circuit? On which factors does the voltage division depend?

• The above questions are the few important things that normally strike a person’s mind who observes the given circuit.
• We’ll see that as we find the answers to the above questions we’ll conclude that the above circuit is a CAPACITIVE VOLTAGE DIVIDER.

Capacitive Voltage Divider This is a kind of voltage divider circuit where capacitors are used as the voltage-dividing components.

Let’s see how the voltage is divided in capacitors

Voltage division in capacitors In a series capacitor circuit, the voltage across each capacitor is different.

• We can easily find the voltage across each capacitor by using the formula C = Q / V
• Q=C/V, for series connection, the charge is constant for all capacitors.
• Capacitor and voltage are in an inversely proportional relation. The higher capacitor has less voltage. From dividing rule
  V=Q/C

The equation for capacitors connected in series

Working of Capacitive voltage Divider

• • • • 3uF capacitor’s reactance XC1 = 1/2πfC1
        = 1/(2*3.142*12000*3*10^-6)
        = 10^6/226224
        = 4.420Ω
      • 1uF capacitor reactance XC2 = 1/2πfC2
        = 1/(2*3.142*12000*1*10^-6)
        = 10^6/75408
        = 13.26Ω
      • The circuit’s complete capacitive reactance XC= XC1+ XC2
        = 4.420Ω + 13.26Ω = 17.68 Ohms.
      • Current I = V/XC
        = 9V/17.68Ω
        =0.50mA
      • The voltage drop across every capacitor is,
        VC1 = I*C1
        = 0.50mA*4.420Ω = 2.21V
      • VC2 = I*C2
        = 0.50mA*13.26Ω = 6.63V

Note Other capacitive voltage divider formulas can also be used

CT = (C1*C2) /(C1+C2)

XCT = 1/2πfCT

Applications of Capacitive voltage Divider

• It can be used to reduce voltage to measure high-level voltage.
• It can measure the resistance of the sensors.
• In electron beam accelerators capacitive voltage dividers are used as capacitive touch sensitive screens.
• They are used to measure fast pulse signals.