A Darlington pair sensor is disclosed. The Darlington pair sensor has an amplifying/horizontal bipolar junction transistor (BJT) and a sensing/vertical BJT and can be used as a biosensor.

The amplifying bipolar junction transistor (BJT) is horizontally disposed on a substrate. The amplifying BJT has a horizontal emitter, a horizontal base, a horizontal collector, and a common extrinsic base/collector. The common extrinsic base/collector is an extrinsic base for the amplifying BJT.

The sensing BJT has a vertical orientation with respect to the amplifying BJT. The sensing BJT has a vertical emitter, a vertical base, an extrinsic vertical base, and the common extrinsic base/collector (in common with the amplifying BJT). The common extrinsic base/collector acts as the sensing BJT collector. The extrinsic vertical base is separated into a left extrinsic vertical base and a right extrinsic vertical base giving the sensing BJT has two separated (dual) bases, a sensing base and a control base.

The Darlington pair sensor has high in-situ signal amplification with low noise and uses substrate space effectively.

A conversion circuit is arranged for converting an ion detection current (i.sub.D) produced by an ion detector into an ion detection signal (P). The conversion circuit comprises: an input stage for converting the ion detection current (i.sub.D) into an ion detection voltage (V.sub.D), an output stage for converting the ion detection voltage into the detection signal (P), the output stage being arranged for drawing a first current dependent on the ion detection voltage, and a supplementary stage for providing a second current (i.sub.S) dependent on the ion detection voltage to the output stage.

The second current may be substantially equal to the first current.

A Darlington pair sensor is disclosed. The Darlington pair sensor has an amplifying/horizontal bipolar junction transistor (BJT) and a sensing/vertical BJT and can be used as a biosensor. The amplifying bipolar junction transistor (BJT) is horizontally disposed on a substrate. The amplifying BJT has a horizontal emitter, a horizontal base, a horizontal collector, and a common extrinsic base/collector. The common extrinsic base/collector is an extrinsic base for the amplifying BJT. The sensing BJT has a vertical orientation with respect to the amplifying BJT. The sensing BJT has a vertical emitter, a vertical base, an extrinsic vertical base, and the common extrinsic base/collector (in common with the amplifying BJT). The common extrinsic base/collector acts as the sensing BJT collector. The extrinsic vertical base is separated into a left extrinsic vertical base and a right extrinsic vertical base giving the sensing BJT has two separated (dual) bases, a sensing base and a control base. The Darlington pair sensor has high in-situ signal amplification with low noise and uses substrate space effectively.