Fixed Frequency Filter - Low/high/band pass, 4th-8th order Butterworth, Chebychev or Bessel response
This module includes 4 single amplifier blocks which could be configured to provide up to 4 bi-quadratic, low-pass or high-pass, filter stages. Each stage is realised in Sallen and Key circuit configuration. The 1st block is preceeded by a passive R-C stage which can be used as a 1st order 'roofing' filter to prevent high frequency components from entering the op-amp. Additionally, the passive RC stage could be used to make the overall filter an odd order. Stages not being used for filtering can be used as buffers/gain stages. This module can now be purchased in a 2x4th order package, which allows the user to implement 2 completely seperate 4th order filters or a single 8th order filter on the one module. The module can also be purchased ready built to the customers own specification.
Features:
- Uses standard 14-pin quad op-amp giving wide choice of, for example, low power, low noise, rail-to-rail input/output or high bandwidth
- Provision for accurate determination of DC gain on the last stage to combat sensitivity of Q to stage gain errors in higher Q stages realised with the Sallen and Key circuit topology. Please note that due to the above sensitivity, we recommend confining low-pass and high-pass filters no more than 6th order (with this Sallen and Key topology) for Chebyshev, 7th order for Butterworth and 8th order for Linear Phase. Band-Pass filters are limited to 1x4th order per module.
Applications:
- Anti-aliasing filter on its own or in conjunction with a tuneable switched capacitor filter - for example, our module based on the LTC 1569, 10th order, low-pass, switched capacitor filter chip
- Reconstruction filter following a digital filter or a switched capacitor filter
- Audio
- Instrumentation
Price: £40 per module
For further information download our datasheet - TAF004-1.pdf