| Nanopore DNA sequencing technology is still a new technology in our country. But it developed quickly. It has become a rapid, high-throughput method of DNA sequencing in the new era. It has a great potential in its development.The core of nanopore DNA sequencing technology is to detect a single molecule of DNA passing through the nanopore. The difference of ionic current caused by the passing through event is usually in the pico-amp (pA) even to femto-amp (fA) level. It is within the scope of micro-current transformation. This paper aims to study the preamplifier applied to nanopore DNA sequencing. The preamplifier will convert the micro-current signal into an appropriate voltage signal. The structure of the preamplifier was using a single resistive feedback Ⅰ-Ⅴ converter. It’s mainly discussed in this paper. The low bias current Op Amp AD549was directly connected to the recording electrode. The gain of the preamplifier could reach1mV/pA. When using resistive feedback preamplifier, the parasitic capacitance of the feedback resistor would destroy the original dynamic characteristics of the system. In addition, the bias voltage, the electrode capacitor, the membrane capacitor, the series resistor appears during the experiment will introduce the pseudo-error signal into the system so that the accuracy of DNA sequencing will be affected. Therefore related compensations need to be taken in order to reduce the noise as far as possible when recoding.In order to solve the problems above, In this paper, the high-frequency compensation was designed to improve the dynamic characteristics of the system. And the capacitance compensation was designed for the parasitic capacitance specially. By the way of simulation in Multisim, the compensations had meted their effects. Three voltage compensations and two drop compensations were also designed for the bias voltage and the series resistor respectively. The low-pass filter was designed for the signal processing after the preamplifier. |
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