SBOU192 July   2017

 

  1.   DIYAMP-SC70-EVM
    1.     Trademarks
    2. 1 Introduction
      1. 1.1 DIYAMP-SC70-EVM Kit Contents
      2. 1.2 EVM Features
      3. 1.3 List of Circuits on the EVM
    3. 2 Hardware Setup
      1. 2.1 EVM Circuit Locations
      2. 2.2 EVM Assembly Instructions
    4. 3 Schematic and PCB Layout
      1. 3.1  Schematic PCB Drawing
      2. 3.2  Single-Supply, Multiple Feedback Filter
      3. 3.3  Single-Supply, Sallen-Key Filter
      4. 3.4  Single-Supply, Non-Inverting Amplifier
      5. 3.5  Single-Supply, Inverting Amplifier
      6. 3.6  Difference Amplifier
      7. 3.7  Dual-Supply, Multiple Feedback Filter
      8. 3.8  Dual-Supply, Sallen-Key Filter
      9. 3.9  Inverting Comparator
      10. 3.10 Non-Inverting Comparator
      11. 3.11 Riso With Dual Feedback
      12. 3.12 Dual-Supply, Non-Inverting Amplifier
      13. 3.13 Dual-Supply, Inverting Amplifier
    5. 4 Connections
      1. 4.1 Inputs and Outputs
      2. 4.2 Power
      3. 4.3 Enable and Disable Feature
    6. 5 Bill of Materials and Reference
      1. 5.1 Bill of Materials
      2. 5.2 Reference

3.2 Single-Supply, Multiple Feedback Filter

Figure 9 shows the schematic for the single-supply, multiple feedback (MFB) filter circuit configuration.

fig02_sbou162.pngFigure 9. Single-Supply, Multiple Feedback Filter Schematic

The MFB topology (sometimes called infinite gain or Rauch) is often preferred, due to low sensitivity to component variations. The MFB topology creates an inverting second-order stage. This inversion may, or may not, be a concern in the filter application.

The single-supply, MFB filter circuit can be configured as a low-pass filter, high-pass filter, or band-pass filter based on the component selection of Z1 through Z5. Table 3 displays the type of passive component that should be chosen for Z1 through Z5 for each filter configuration.

Table 3. MFB Filter Type Component Selection

Pass-Band
Filter Type		 Type of Component (Z1) Type of Component (Z2) Type of Component (Z3) Type of Component (Z4) Type of Component (Z5)
Low Pass R1 C2 R3 R4 C5
High Pass C1 R2 C3 C4 R5
Band Pass R1 R2 C3 C4 R5

For additional guidance in designing a filter, download FilterPro™ active filter design software.

Capacitor C2 provides the option to filter noise that may be introduced from the Vref input. calculates the cutoff frequency due to C2.

Equation 1. nneq01_sbou162.gif

The PCB layout of the top layer of the single-supply, MFB filter configuration is displayed in Figure 10.

fig09_sbou162.gifFigure 10. Single-Supply, MFB Filter Top Layer

The PCB layout of the bottom layer of the single-supply, MFB filter configuration is displayed in Figure 11.

fig11_sbou162.gifFigure 11. Single-Supply, MFB Filter Bottom Layer