## Advantages of Pi filter circuit | Disadvantages of Pi filter

This page describes Pi filter circuit schematic and its working. It mentions benefits or advantages of Pi filter and drawbacks or disadvantages of Pi filter.

**Introduction :**
There are three basic impedance matching filters viz. L network, T network and π network.
L network is easy to implement due to its two components requirement.
Moreover L network do not change Q of the circuit.
T and π networks are more complex compare to L network but they are preferred as they
generate higher output voltages with low ripple factors.

### What is Pi Filter ?

The network which has components (L, C, R) connected in the form of a π shape is called pi network. The filtering device which uses L and C in the π shape is called Pi filter. It can be used both as full wave and half wave rectifiers.

The figure-2 depicts use of Pi filter as LPF (Low Pass Filter) and HPF (High Pass Filter). In LPF configuration, two capacitors are connected in parallel of input and output where as a inductor is connected in series. In HPF configuration, two inductors are connected in parallel of input and output where as a capacitor is connected in series.

Following are the mathematical equations of a Pi filter as LPF.

• Cut off frequency, Fc = 1/(π*(L*C)^{1/2})

• C value i.e. C1 and C2 = 1/(Z0*πFc)

• L value i.e. L1 = Z0/(π*Fc)

Where Z0 is characteristic impedance with value of 50 Ohm or 75 Ohm.

Following are the mathematical equations of a Pi filter as HPF.

• Cut off frequency, Fc = 1/(4*π*(L*C)^{1/2})

• C value i.e. C1 = 1/(4*Z0*π*Fc)

• L value i.e. L1 and L2 = Z0/(4*πFc)

Where Z0 is characteristic impedance with value of 50 Ohm or 75 Ohm.

### Benefits or advantages of Pi filter

Following are the benefits or **advantages of Pi filter**:

➨It is very easy to implement in RF circuit designs.

➨It is easy to replace these three components due to its easy access for de-soldering and re-soldering.

➨It provides higher output DC voltages.

➨It delivers output with much lower AC ripples.

➨It offers better load regulation compare to L type filter.

### Drawbacks or disadvantages of Pi filter

Following are the drawbacks or **disadvantages of Pi filter**:

➨Pi filter requires higher value capacitors which make them bulky. This is a major concern for space constraint designs.

➨Pi filters are not suitable when load current varies as they offer poor voltage regulation.

➨Pi filter is not suitable for high current flow through it. This makes series inductors bulky as well as expensive.

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