FIELD

The present technology relates to a high sensitivity sensor. More specifically, the present technology relates to a high sensitivity photodetector with a high-gain transimpedance amplifier.

BACKGROUND

Monitoring electrical activity and Ca2+transients in biological tissues and individual cells increasingly utilizes optical sensors based on voltage-dependent and Ca2+dependent fluorescent dyes. However, achieving satisfactory signal-to-noise ratios (SNR) often requires increased illumination intensities and/or dye concentrations, which results in photo-toxicity, photobleaching, and other adverse effects limiting the utility of optical recordings. Most challenging are the recordings from individual cardiac myocytes and neurons.

Current transimpedance amplifiers used to amplify fluorescent signals from individual cells are insufficiently sensitive, while other types of single-channel photodetectors are prohibitively expensive. High-gain transimpedance amplifiers rely on a high-impedance (>1 GΩ) resistive element in the feedback path to achieve high gain. The key issues that diminish their performance in photo detection are parasitic capacitance, which makes it difficult to achieve the same bandwidth from one circuit to another, cross-talk and capacitive coupling (high-impedance circuits are by nature very susceptible to coupling from or to neighboring circuits), and the difficulty in optimizing the circuit elements to minimize noise (every noise source in the circuit will have a weighted contribution, and therefore none can be neglected). Thus, there is a need for an low-cost, high-sensitivity photodetector incorporating a high-gain transimpedance amplifier.

The present technology is directed to overcoming these and other deficiencies in the art.

SUMMARY

One aspect of the present technology relates to a device. The device includes a sensor having an anode and a cathode. An operational amplifier (op-amp) having a single-ended output terminal, a non-inverting input, and an inverting input, is operatively coupled to one of the anode or the cathode of the sensor by the inverting input. A feedback resistor having a resistance of at least approximately one giga-ohm (1 GΩ) is operatively coupled between the single-ended output terminal and the inverting input of the op-amp. A grounded field shunt is positioned adjacent to the feedback resistor. The op-amp, grounded field shunt, and feedback resistor are disposed within an electrical shield enclosure. The single-ended output terminal of the op-amp terminates outside of the electrical shield enclosure.

Another aspect of the present technology relates to a method of measuring a feature of a signal using the device. The signal to be measured is received by the sensor. An amplified signal based on the received signal is output at the single-ended output terminal of the op-amp. At least one feature of the signal is measured based on the amplified signal.

The high sensitivity photodetector with high-gain transimpedance amplifier of the present technology comprises a circuit topology for a simple, inexpensive, but highly sensitive photodetector with a high-gain transimpedance amplifier that can be used to detect and amplify faint optical signals such as the fluorescent signal emitted by voltage-sensitive fluorescent dyes in cardiac cells. The topology is a novel combination of existing circuit elements and shielding which enables the very low current generated by photons hitting the photodetector to be amplified and converted to a useable voltage that can be provided as an input for various measurements.

