ANALOG DEVICES DC675C Demonstration Board, LT1568, Fourth Order, RC Filter Building Block

DC675C is a demonstration circuit for the evaluation of filter circuits using an LT®1568. The LT1568 is a dual 2nd order active-RC filter building block with precision ±0.75% capacitors and low noise op amps with 180MHz GBW trimmed to ±10% maximum variation. The ±10% GBW variation of the LT1568 op amps allows for minimizing the higher frequency error by decreasing resistor values. The cutoff or centre frequency (fC) range of an LT1568 filter is 200KHz to 10MHz (5MHz for a bandpass filter). The low limit of 200KHz was chosen only to minimize resistor noise and DC offsets (using external capacitors the fC frequency can be less than 200KHz). For testing and evaluation, the DC675C assembly is configured as a single 4th order, 500KHz narrow passband bandpass filter.

• Total supply voltage range from 2.7 to 11V
• 35mA max supply current at VS = 3V, TA = 25°C
• 0.5µA typ op-amp input bias current at TA = 25°C
• 1.4nV/?Hz typ OA input voltage noise density at f =100KHz, TA = 25°C
• 1.0pA/?Hz OA input voltage noise density f =100KHz, TA =25°C