Microchip Technology MCP6XXXDM-FLTR User Manual

© 2006 Microchip Technology Inc.

DS51614A-page 31

This appendix contains the schematics and layouts for the different pieces of the Active 
Filter Demo Board Kit Sub-assemblies:
• V

DD

/2 Filter Section (Sub-Assembly # : 102-00098R1)

• Active Filter Section (Sub-Assembly # : 102-00097R1)
• Accessory Bag (Sub-Assembly # : 110-00097R1)

See Figure A-1 for the V

DD

/2 Filter Section circuit diagram. The input and output 

headers (J1, J2, P1, and P2) allow the PCBs to be cascaded as needed. The filter order 
will determine how many of the Active Filter Section boards need to be cascaded.
R1, R2, and C3 produce a V

DD

/2 reference voltage. The op amp U1 buffers this 

reference voltage, and is set to unity gain. U1 must drive the impedances connected to 
it on all of the Active Filter Section. Op amp U1 is usually a single, PDIP-8 part inserted 
into the DIP-8 socket; it can be a SOIC-8 that is soldered to the board (see U1A in 
Figure A-1).
C1 and C2 are bypass capacitors for V

DD

.

The demonstration board includes five test points for convenience on the bench. TP1 
and TP2 make it possible to connect a function generator to the filter input; this signal 
is passed on to the other boards. TP3 through TP5 provide connections for external 
power supplies, which are also passed on to the other boards.
JP1 allows the user to choose the V

DD

/2 reference voltage source:

• A lab supply (EXT = External V

DD

/2 source)

• Op amp U1’s output (INT = Internal V

DD

/2 source)

/2 Filter Section BOMs” for the Bill of Material for this kit.