Hi everyone.. We have first order low pass filter using simple resistor and capacitor (passive realization). If we design the same filter using op-amp (active realization), then how can we say (and verify in PSPICE OrCad tool) active realization better than passive realization ?
Hi SungWon, please see the below attached images of first order LPF. One image is LPF by active realization and other one by passive. From these, two figures active requires one extra block (op-amp). So, area and cost of the active design is high compare to passive. Even, we prefer active realization because active realizations improve power gain, avoids loading effect, etc. But my question is, how can I verify these advantages in PSPICE OrCad tool?
Since you use LPF, You can simulate both filters ( active and pasive ) with harmonics voltage source and use resistive load. Then try to change the load properties for example load is 10 Ohm, change to 5 Ohm or 1000 Ohm. You can see the different from filtering results, for example from the ripple voltage output. In addition, Compared to active filters, properties of passive filters may change significantly when the load is changed. In comparison, properties of active filters do not change a great deal when the load is changed, since power can be added to the circuit by the active components. This is the advantages of active filter over the passive ones.
Hope this my help you :)
For a simple RC low-pass filter, the active filter adds noise, offset error and other 'problems'. The only advantage is that it removes the influence of the load resistance (imagine an R parallel to the capacitor) from the filter and allows for a variety of load resistance valures without having to adapt the filer component values.
Advantages start to become significant when regarding other filters: a high-pass can be realized by implementing a low-pass filter (which is less critical by design) in the feedback path. And active filters allow for the more complex filter design schemes...
Hope this helps a bit
Try to solve higher-order RC filters without active elements (and inductors).
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering