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

3.6 Difference Amplifier

Figure 21 shows the schematic for the difference amplifier circuit configuration.

fig14_sbou162.pngFigure 21. Difference Amplifier Schematic

The difference amplifier utilizes both inverting and non-inverting inputs and produces an output that is equal to the difference between the inputs. The gain of the difference amplifier is dependent on the ratio of the resistor values selected.

Equation 15 displays the transfer function of the difference amplifier circuit configuration.

Equation 15. nneq15_sbou162.gif

If R1 = R4 and R2 = R3, Equation 15 can be simplified to Equation 16.

Equation 16. eq25_sbou162.gif

Capacitors C1 and C4 provide the option to filter the output of the amplifier. The cutoff frequency of the filter can be calculated using Equation 17.

Equation 17. neq30_sbou162.gif

    where

  • R1 = R4, R2 = R3, and C1 = C4

The PCB layout of the top layer of the difference amplifier circuit configuration is displayed in Figure 22.

diyamp_nfig22_diff_amp_toplayer.pngFigure 22. Difference Amplifier Top Layer

The PCB layout of the bottom layer of the difference amplifier circuit configuration is displayed in Figure 23.

diyamp_nfig23_diff_amp_bottomlayer.pngFigure 23. Difference Amplifier Bottom Layer