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A German university has developed a charge-sensitive amplifier whose sensitivity and bandwidth are about 50 times higher than conventional amplifier circuits and which does not require cooling like other approaches.
The university offers a license and a research cooperation agreement.
Measuring small electrical charges and low voltages often poses a challenge to industry. A charge-sensitive amplifier has now been developed at a German university. It enables an electronic circuit to amplify the lowest voltages. It is suitable for the usual applications of an electrometer. This allows voltage and charge measurements on high impedance power sources. Due to the higher sensitivity and the very high bandwidth of the circuit additional applications are possible, where previous measuring devices were not sufficient.
Two junction gate field-effect transistors (JFETs) form a differential common-source input stage whose outputs lead via a follower emitter to an operational amplifier. In contrast to conventional circuits there is no negative feedback on the input by a high-impedance resistor. The leakage current of the FET at the input is compensated by the leakage current of an equivalent FET with the same temperature dependence. This results in an extremely high input impedance. The leakage current compensation is combined with a “bootstrap circuit”, which ensures a high bandwidth.
The charge-sensitive amplifier which is available as a prototype can as well be operated as a voltage amplifier with an input capacitance of approx. 5 pF (programmable frequency) and an extremely high impedance. The circuit provides high sensitivity with sufficient drift stability to conduct measurements in the range of over a one second time. The bandwidth is about 1 MHz. Comparable charge amplifiers with similar sensitivity are intended for short pulses only and therefore not suitable for quasi-static measurements. On the other hand, there are electrometers with a very low bandwidth. This circuit closes this metrological gap. The input circuit with the combination of junction FETs is without any further assembly, intrinsically protected against electrostatic charge.
The university offers a license or a research cooperation agreement to industrial partners, who would like to make use of the technology. The innovation is aimed at companies in measurement technology and diagnostics (in sensitive units of measurement). A research cooperation is appropriate if there is interest in bringing the process to a higher technology level in cooperation with the university.
The sensitivity and bandwidth compared to conventional amplifier circuits is approx. a factor of 50 higher and, in contrast to other technological approaches, does not require any cooling. In the field of measurement technology, measurement tasks in the application fields of physics, chemistry, biology and medicine can be realised easily and cost-effectively.
The university is holder of a patent application in Germany. International registrations are still possible.
The development is aimed at industries or end users from the fields of physics, chemistry, biology and medicine. Extremely small electrical charges or voltages often have to be measured for diagnostic purposes, among other things. This makes the technology interesting for companies that produce very sensitive measurement technology or devices and layers in these fields of application.The university offers a licence agreement.
If the company is interested in jointly developing the invention into a product (e.g. within the framework of R&D projects), a research cooperation is also advisable. In this context, it is also possible to verify technical properties for the company or to bring the invention to a higher technological level.