Transistor analogy

Analog in-circuit test addresses testing for shorts in the printed wire circuitry analog components, passive devices such as resistors, inductors, and capacitors and simple semiconductor components such as diodes and transistors. Analog in-circuit testing is conducted without applying power to a board that is, it is an unpowered test methodology. 

Fig. 31 Proposed unimolecular amplifier DiD2A, in a circuit analogous to a grounded-emitter junction transistor, grounded-source FET, or grounded-cathode triode circuit. The arrows show the direction of preferred electron flow. The two Au and one A1 electrode tips must be about 3 nm apart...

As demonstrated above, the heat current from D to S can be switched between different values. However, in many cases, like in an analog circuit, we need to continuously adjust the current Js and/or Jo in a wide range by adjusting the control temperature Tg. In Fig.11 we demonstrate this modulator/amplifier function of our transistor. The basic mechanism of such modulator/amplifier is the same as that of the switch but we consider here different parameter values. It is seen that in the temperature interval Tq (0.05,0.135), the heat current through the segment G remains very small ((—10-5 10-5), within the shadow strip in Fig. 10, while the heat currents Js and Jg continuously increase from 5 x 10-5 to 2 x 10-4. 

The first monolithic devices have been presented at the same time by a group at NIST and a group at the Physical Electronics Laboratory (PEL) of ETH Zurich [77-81]. The NIST chip hosts an array of microhotplates integrated with transistor switches and a readout amplifier for the sensitive layer. The device presented by PEL includes an analog temperature controller and a logarithmic converter for reading out the sensor values. This was the first monolithic realization of an embedded system architecture with integrated microhotplate. 

The coefficients of thermal resistance can either be measured for existing devices or be calculated with the thermal microhotplate model presented in Chap. 3. In analogy to resistor-heated membranes, the model can be used for evaluation and optimization of new designs. A combination of the presented transistor model equations with the lumped microhotplate model in Sect. 3.4 would allow to also derive an AHDL model for coupled-system simulations. 

Researchers (Benilova et al., 2006 Arkhypova et al., 2008) are developing a biosensor-based pH-sensitive field-effect transistor technology for rapid determination of glycoalkaloids. The test takes advantage of the anticholinesterase activity of the glycoalkaloids. These tests could hold great promise, analogous to the ELISA test mentioned above. 

Thin polymer films have many possible technical applications. Transistors and light-emitting diodes are the obvious ones. In ultra-thin films, one may even approach an electronics of molecular dimension. Molecular electronics will be a future challenge for basic and applied science. Nature applies it on a large scale in the reaction centers of the photosynthetic process, where photoinduced mobile charges are separated in some analogy to the separation of the photo-(p-n)-pair in the junction zone of a semiconductor (see Section 13.3.1). 

The function of the complementary p-n-p transistor may be explained by analogy to the n-p-n transistor by reversing polarities and considering hole rather than electron transport (7, 8). In addition, a large variety of... 

Fig. 6.22 Analog circuits for operation of ion-sensitive field-effect transistor (ISFET) (a) in constant applied voltage mode ((6.62) and (6.63)) and (b) in (source-follower) constant current feedback mode ((6.65) and (6.69))...

Combining (6.98), (C.19b), and (C.26) yields dependence of Vq on partial pressure of the donor-acceptor gas. In direct analogy with ISFET operation in the presence of interfering ions (6.71) we can write the following for the transistor in some arbitrary gas phase and the analyte. 

Local resolution can also be obtained by frequency variation, if a higher-dimensional electrochemical chain is constructed (analogous to the construction of a field effect transistor)298 such as... 

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