No abstract
THE CHARGE-TRANSFER split-electrode structure"' has two major limitations which result in inadequate performance in some applications. It requires two operational amplifiers to clamp the two sensing electrodes to a virtual reference voltage. A third amplifier is needed to obtain the differential signal. Improved approaches3y4 have been reported. However, a complex chargesensing circuitry is still required. A complementary chargesensing approach using charge-coupled device technology will be described in this paper. The approach only needs simple sensing circuitry, requires no contacts over gate-oxide and achieves a zero common-mode condition. Zero common-mode was reportedly achieved5 but a bucket-brigade was used and contact over gate-oxide was needed.The filter consists of a positive and a negative CCD channel; Figure 1. Only the first stage of the positive channel is a twophase structure. The remaining stages of both channels are operated in an 1%-phase clocking mode. The dc-phase electrodes are split for tap-weight implementation. The outer portions of the split-electrodes are connected to vdc and the inner portions are connected to the charge-sensing line. The input stages of both channels are identical so that matched input can be sampled. The charge-sensing concept of the filter is based on a well known physical phenomenon. Electrons entering a CCD potential-well will induce positive charge on the CCD electrode and electrons leaving the potential-well will induce negative charge. Charges sampled by the input-gates in each channel will first reside beneath @la and $qb simultaneously. The charge in the negative channel will then be transferred to the first split-electrode while the two-phase stage in the positive channel transfers its charge to @2a. During the next phase-clock transition, the charge in the negative channel will leave the split-electrodes and the charge in the positive channel will enter the split-electrodes. The resultant displacement current spike in the charge-sensing line will be converted to a voltage-step by an operational amplifier. The operational amplifier will be reset in the next half cycle of the phase-clock; see timing diagram in Figure 1.Since the charge to be sensed is already the difference between the positive and the negative tap-weights, only one operational amplifier charge-sensing circuit is needed and the dynamic range should be improved significantly. The filter is operated by a pair of complementary phase clocks. The clock-feedthrough into the charge-sensing line can, to a large extent, be cancelled by matching the overlap between phase-clock electrodes and the chargesensing electrodes. Due to the double-channel configuration, no contact is needed over the gate-oxide. This is an important advantage over the bucket-brigade approach and the double-split approach.The major speed limitation of an operational amplifier is that the amplifier consists of two gain stages and a pole-split compensation capacitor. The unity gain frequency of the operational amplifier is limited t ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.