Choose a direct capacitance solve, a simplified BJT filter estimate, or a series/parallel total. Units range from pF to F. The BJT filter is unregulated and its assumptions are shown with the result.

Multiply a known input capacitance by a positive dimensionless multiplier.

Use a positive capacitance. Changing units converts the entered quantity.

Positive dimensionless ratio. It does not specify a circuit topology.

Result unit

Default: ยตF. Selected unit still applies when collapsed.

Capacitance Multiplier Formula

The following formula is used to calculate the output capacitance:

Cโ‚’แตคโ‚œ = Cแตขโ‚™ ร— M

Variables:

  • C_out is the output capacitance (ฮผF)
  • C_in is the input capacitance (ฮผF)
  • M is the multiplier

To calculate the output capacitance, multiply the input capacitance by the multiplier.

What is a Capacitance Multiplier?

A capacitance multiplier is an electronic circuit that uses an active device (like a transistor) to make a small capacitor function like a capacitor that is much larger. This is useful in power supply filters where large capacitance values are needed to reduce ripple voltage but physical size or cost of large capacitors is prohibitive.

How to Calculate Output Capacitance?

Choose Direct: output capacitance, enter the input capacitance and multiplier, then select Calculate. The following steps describe that solve.

  1. First, determine the input capacitance (C_in) in microfarads (ฮผF).
  2. Next, determine the multiplier (M).
  3. Use the formula from above = C_out = C_in * M.
  4. Finally, calculate the output capacitance (C_out) in microfarads (ฮผF).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Input capacitance (C_in) = 100 ฮผF

Multiplier (M) = 10; output capacitance = 100 ร— 10 = 1,000 ฮผF.

The BJT estimate assumes a single base resistor and capacitor feeding an NPN emitter follower with constant load current. It includes base-current resistor drop and an assumed base-emitter drop. A desired output is a comparison, not a regulated setpoint. Ripple uses an ideal RC sinusoidal estimate and is unavailable when forward-active operation is not supported. Dissipation is estimated at the supplied low DC input, not a maximum thermal rating. See Analog Devicesโ€™ circuit explanation.