JPH02280047A - One-chip semiconductor biosensor - Google Patents

Abstract

PURPOSE:To reduce the area of an external circuit, and also, to inhibit the influence of an external noise by integrating a source follower circuit for driving an FET of a sensor part, a differential amplifier for inputting each source potential and a differentiating circuit. CONSTITUTION:A source follower circuit 2 supplies a constant-voltage and a constant-current to between a drain 5 and a source 7 of an enzyme film (EN) FET, and between a drain 6 and a source 8 of an (RE) FET for reference, respectively and drives the ENFET and the REFET. Also, a differential amplifier 3 inputs a source potential difference of the ENFET and the REFET, and a differentiating circuit 4 inputs an output voltage of the differential amplifier 3 and outputs an output speed of a sensor to a signal output terminal 10. In such a way, by integrating an analog circuit required for a semiconductor biosensor to one chip, an external circuit becomes unnecessary, an area of the external circuit becomes unnecessary, and also, the influence by an external noise is suppressed to the minimum.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a one-chip semiconductor device with a built-in analog circuit that integrates a sensor section, a sensor drive circuit, a differential amplifier, and a differentiation circuit into a 1,000-amp unit. Regarding iosensor.

[Prior Art] A conventional semiconductor biosensor has only a sensor section made up of two field effect transistors, drives the sensor section by an external circuit, and outputs a sensor output signal to the external circuit. That is, the sensor output signal, which is the potential difference between the sources of two field effect transistors, is input to a differential amplifier provided in an external circuit, digitized by an A/D converter, and calculated and controlled by a microcomputer. It is carried out.

[Problems to be Solved by the Invention] Conventional semiconductor biosensors have the above-mentioned configuration, so that: ■ The area of the analog circuit in the external circuit increases; ■ Noise increases due to the mixture of analog' and digital; ■ There is a drawback that the routing of the ground (earth) line within the circuit pattern is limited.

Additionally, it takes several tens of seconds for the biosensor and the object to be measured to react, the sensor output increases, and reaches a steady state, so it is necessary to wait for the reaction between the sensor and the object to be measured during this time. There is a drawback.

[Means for Solving the Problems] A one-chip semiconductor biosensor with a built-in analog circuit according to the present invention includes: a sensor section consisting of a reference field effect transistor and an enzyme membrane field effect transistor; and a sensor section that drives the field effect transistor. The present invention is characterized in that a source follower circuit for, a differential amplifier receiving each source potential of the field effect transistor as input, and a differentiating circuit receiving the output of the differential amplifier as input are integrated on one chip.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a one-chip semiconductor biosensor 1 with a built-in analog circuit according to the present invention.

In the figure, a source follower circuit 2 is connected between the drain 5 and source 7 of an enzyme membrane field effect transistor (hereinafter referred to as ENFET) and between the drain 6 and source 8 of a reference field effect transistor (hereinafter referred to as REFET). A constant voltage and a constant current are supplied between each of them to drive the ENFET and REFET.

As the reaction between the object to be measured and the ENFET progresses, the difference between the source potential VE of the ENFET and the source potential vR of the REFET increases. This potential difference is proportional to the concentration of the object to be measured.

The differential amplifier 3 uses this potential difference (VE-VR) as a human horn and outputs a voltage α (VE-vR) multiplied by α.

The differentiating circuit 4 inputs the output voltage of the differential amplifier 3 and outputs the sensor output speed α(VE-VR)/Δ1 (1 is time), which is obtained from the signal output terminal 10.

This voltage is based on the reference electrode terminal 11, and the reference electrode terminal 11 is short-circuited to the reference electrode 9 that detects the potential of the liquid containing the object to be measured.

FIG. 2(a) is an output characteristic diagram of the sensor shown above at the same time. The output voltage α (VE VR) of the differential amplifier 3 increases with the passage of time, reaches a steady state at time A, and no longer increases.

FIG. 2(b) is an output speed characteristic diagram of the sensor.

As time passes, the output speed α(VE-vR)/Δt increases rapidly, reaches a peak at time B, and then decreases.

The peak value of this output speed is in a proportional relationship with the steady value of the differential output, and is therefore also in a proportional relationship with the concentration of the liquid containing the object to be measured. Since the relationship of time A> time B always holds, the concentration of the object to be measured can be determined more quickly than in the conventional method using differential output, for example, it is possible to determine the concentration within about 10 degrees. It is.

[Effects of the Invention] As explained above, according to the present invention, by incorporating the necessary analog circuits into the semiconductor biosensor, an external circuit part becomes unnecessary, the area of the external circuit is reduced, Its packaging density is reduced.

Furthermore, the influence of external noise can be minimized by integrating the built-in analog circuits.

Further, by extracting the voltage obtained by differentiating the differential output with the differentiating circuit to the output terminal, there is an effect that the concentration of the object to be measured can be detected quickly.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing the output characteristics of the sensor. 1... One-chip semiconductor biosensor with built-in analog circuit 2... Source follower circuit 3... Differential amplifier 4... Differential circuit 5... Drain of enzyme membrane field effect transistor (ENFET) 6...・Drain 7 of reference field effect transistor (REFET)... Source 8 of ENFET... Source of REFET

Claims (1)

[Claims] A sensor section comprising a reference field effect transistor and an enzyme membrane field effect transistor; a source follower circuit for driving the field effect transistor; and input source potentials of the field effect transistors. A one-chip semiconductor biosensor with a built-in analog circuit, characterized in that a differential amplifier and a differential circuit that receives the output of the differential amplifier as input are integrated on one chip.