In this study, transimpedance amplifier based front-end circuits which can be employed to measure small capacitances were designed, analyzed and simulated using analog electronic circuit simulator. The front-end circuit converts the current flowing through the measured capacitance into a modulated voltage value which contains information regarding the desired capacitance. The frequency-domain, time-domain, stability and noise analyzes were carried out numerically and in simulation environment using a circuit simulator. The analytical, numerical and simulation results can be used to design optimized, precise and stable transimpedance amplifiers with low-noise value. The measured capacitance value was 10 pF which is low enough to simulate various real-world applications. Three commercially available, off-the-shelf operational amplifiers with different peripheral passive components were employed for computer based analysis. The designed transimpedance amplifiers are suitable to connect with capacitance extraction circuits which use analog or digital demodulation techniques.
This paper presents a novel and secure image encryption method. The plain image’s pixels are confused using the N-point crossover operation of genetic algorithms. Randomly paired rows and columns are determined by the two state variables of a six-dimensional hyperchaotic map. The number of crossover points, which are calculated by the two other state variables of the hyperchaotic map, differ from each other for each row or column pair. The crossover positions are specified according to the number of crossover points with the help of the last two state variables. The proposed algorithm generates the diffusion stage’s encryption key using the SHA-256 hash value of the plain image. Mutation and crossover operators are implemented into the 16-bit subblocks of the 256-bit hash value. Thus, a total of 16 subblocks with the size of 16 bits are employed as the encryption key after the implementation of the genetic operations. The scrambled image’s pixels are altered with the generated encryption key and previously encrypted pixels. Key space and sensitivity, histogram, correlation, information entropy, differential, data loss, noise attack, and computational time analyzes are performed to test the safety and effectiveness of the encryption method. The experiments and simulation results show that the proposed encryption technique is highly secure and efficient since it can resist various attacks. The comparisons with recent works show that this method outperforms many state-of-the-art algorithms in several performance metrics.
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