ProtoBlock Dual Sallen-Key Filter (p/n 970502)

The BrownDog Dual Sallen-Key filter circuit is a printed circuit board on which two complete and independent two-pole filters can be constructed from surface mount components using the Sallen-Key topology. Pads for resistor and capacitor chip components will accommodate either 0805 or 1206 size devices. Because the performance of Sallen-Key filters can be sensitive to component value variations, dual sets of chip component pads connected in parallel are provided on both sides of the board for each filter element; these allow the user to trim to the required values. Using an SO8 dual op-amp with industry standard pinouts (available from many manufacturers), two independent two-pole filters can be fabricated to realize low-pass, band-pass, or high-pass configurations. The filter circuits can be cascaded for higher order responses. The Sallen-Key topology allows the use of current feedback op-amps for high frequency designs.

Power supply decoupling capacitor pads are provided and most of the reverse side of the board serves as a ground plane. The circuit's compact size allows it to be plugged in a 24 pin DIP IC socket (0.600" wide) or any solderless prototyping board.

• Two independent two-pole Sallen-Key filter circuits; can be cascaded with external connection
• Accommodates either 0805 or 1206 chip components
• Uses dual SO8 op-amp IC with industry standard pinout
• Dual parallel sets of pads for filter element components to allow easy trimming
• Power supply decoupling capacitor pads provided
• Ground plane on reverse side
• Same footprint as 0.600" wide 24 pin DIP IC
• Can be used as a generic prototyping adapter for any SO8 IC
• Can be provided with solder tail pins (0.018" diam) or no pins
• Great for IC evaluation
• Download filter circuit schematic:  970502sch.pdf
• Download Texas Instruments Application Report: "Analysis of Sallen-Key Architecture"
• Link to Texas Instruments "Analog Filter Op-amp Design Knowledge Base"