Tunable Filters Using Charge Transfer Devices.
Final rept. 16 Jul 74-15 Dec 75,
TEXAS INSTRUMENTS INC DALLAS CENTRAL RESEARCH LABS
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To date, CCDs have required complicated off-chip peripheral circuitry. The widespread application of CCDs to transversal filtering in systems depends on the integration of these circuits on the CCD chip. This report describes the design and performance of a completely self-contained and integrated 800-stage CCD transversal filter. The device contains the clock generator and drivers as well as the input and output circuits, so that only dc voltages and one master clock signal are required to operate the device. The chip is designed for general filtering applications and can be mask-programmed for a variety of different transfer functions. Its performance as a tunable bandpass filter with a 3 dB bandwidth of 0.7 of the center frequency and 40 dB sidelobe rejection is described. The center of the passband can be tuned from 500 Hz to 500 kHz. Key problems in the integration of the peripheral circuits have been related to the use of standard MOS circuits to perform these functions. To solve these problems, we have designed voltage amplifiers on this device. A CCD type of structure is used to obtain a differential sampled data voltage amplifier. These amplifiers are used both for the input stage and for the differential output of the filter. These amplifiers provide significant advantages over standard MOS circuits including good linearity, high speed, low power, low noise, and stable gain performance. Experimental results obtained with the bandpass filter are compared to predicted performance. Author
- Electrical and Electronic Equipment