Ultraselective, Low Power 8th Order Elliptic Bandpass Filter with Adjustable Gain

The LTC1164-8 is a monolithic ultraselective, 8th order, elliptic bandpass filter. The passband of the LTC1164-8 is tuned with an external clock and the clock-to-center frequency ratio is 100:1. The –3dB pass bandwidth is typically 1% of the filter center frequency. The stopband attenuation of the LTC1164-8 is greater than 50dB. The lower and upper stopband frequencies are less than 0.96 • center frequency and greater than 1.04 • center frequency, respectively.

The LTC1164-8 requires an external op amp and two external resistors (see the circuit below). The filter’s gain at center frequency is set by the ratio RIN/RF. For a gain equal to one and an optimum dynamic range, RF should be set to 61.9k and RIN should be 340k. For gains other than one, RIN = 340k/Gain. Gains up to 1000 are obtainable. Setting the filter’s gain with input resistor RIN does not increase the filter’s wideband noise. The 270μVRMS wideband noise of the LTC1164-8 is independent of the filter’s center frequency.

The LTC1164-8 is available in a 14-pin PDIP or a 16-pin surface mount SO Wide package.

Applications

* Asynchronous Narrowband Signal Detectors

* Low Frequency Asynchronous Demodulators

* Handheld Spectrum Analyzers

* In-Band Tone Signaling Detectors

* Ultraselectivity (50dB Attenuation at ±4% of Center Frequency)

* Adjustable Passband Gain

* Noise Independent of Gain

* Filter Noise: 270μVRMS, VS = Single 5V Supply

* Clock-Tunable (Center Frequency = fCLK/100)

* Center Frequencies up to 5kHz, VS = ±5V (Typical ISUPPLY = 3.2mA)

* Center Frequencies up to 4kHz, VS = Single 5V Supply (Typical ISUPPLY = 2.3mA)