Digital electronic circuits

This enables manipulation of charges in a circuit at the single electron level and therefore to the creation of, e.g., sensitive amplifiers and electrometers, switches, current standards, transistors, ultrafast oscillators, or generally of digital electronic circuits, in which the presence or absence of a single electron at a certain time and place provides the digital information. 

Logic gates are used to control a digital electronics circuit. 

ANALOGUE PROCESSING A method of pulse shaping and measurement using analogue, rather than digital, electronic circuits. Traditional amplifier systems are analogue in nature. 

The previous chapters in this book have concentrated on particular aspects of digital electronic systems design. Of course, in any practical system a whole range of design styles and constructs will be applied. This chapter shows how the tediniques introduced can be used together to develop a reasonably complex digital electronic circuit. 

While the frequency of a signal can be established using an oscilloscope, the accuracy specification for most oscilloscope time bases gives a tolerance figure of 5%. For mai situations this is totally inadequate, as a more precise measurement is required. Fortunately, a sinusoidal wave can easily be converted into a pulse or square wave, which can then be counted by digital electronic circuits. With electronic counting techniques, the frequency of a signal can be determined with a very small tolerance. 

Other analyzers such as the Gilford Automated Enzyme Analyzer and the LKB-8600 Reaction Rate Analyzer analyze discrete samples one at a time. These instruments provide kinetic analyses, digital data reduction at the time each sample is analyzed, and excellent electronic and optical characteristics. Recently, Atwood has developed kinetic enzyme analyzers which require only 9 seconds for measuring an enzyme activity, using highly stable and sensitive electronic circuits (12). This short read out time allows a large number of samples to be processed by one instrument in an automated mode. 

One area of analytical chemistry which is currently developing rapidly is the automation of methods. Some degree of automation has been used for a number of years in instruments such as automatic burettes coupled to absorptiometric or electrometric end-point detectors, and in data output devices which provide continuous pen recording or signal integration facilities. The major features of recent developments include the scope for instrumental improvements provided by solid-state electronic circuits and the increasing application of digital computers (Chapter 13). 

Kimbler, Will. 1994. Practical Digital Electronics for Technicians. Oxford BH Newnes. Markus, John, ed. 1980. Modern Electric Circuit Reference Manual. New York McGraw-Hill. 

In order to assimilate the following mateial, the reader should be familiar with a few simple concepts in instrumentation elecronics. These topics are more than adequately discussed in numerous texts and so we do not belabor them here. For the convenience of those who need to review, we have prepared a list of subjects essential to understanding these introductory sections. This list is all-inclusive, so study of topics not on the list (e.g., ac circuit theory, inductance, transformers, power supplies, digital electronics, transducers, transistors, etc.) will be of no immediate value. 

The experiments are based on analog electronic circuits designed in the usual way [112,126] to model the system of interest, and then driven by appropriate external forces. Their response is measured and analysed digitally to create the statistical quantity of interest which, in the present case, was usually a prehistory probability distribution [60,124]. We again emphasize that such experiments provide a valid test of the theory, and that the theory should in this case be universally applicable to any system described by (16), including natural systems, technological ones, or the electronic models studied here. Some experiments on a model of (17) are now described and discussed as an illustrative example of what can already be achieved. 

Figure 4.26 Possible electronic circuit for deriving one-dimensional position information from a position-sensitive detector with a resistive strip anode. The two charges Q, and Q2 on the ends of the anode are amplified, shaped and converted to a digital signal. The mathematical operations of Q = Qt + Q2 and Q2/Qj are performed electronically, and the result is stored in a histogramming memory from which it is read into the computer. Q2/Q carries the information first that an electron has been detected and second at which position this electron has hit the detector. From [Wac85].

Figure 4.47 Typical electronic circuit for the measurement of electron-electron coincidences with two spectrometers (SP1, SP2) placed at the positions 0 , and 5, , respectively. The pre- and main amplifiers are together represented by a triangle. The delay retards the signal from SP1, thus providing a STOP of the time-to-digital converter (TDC) if this time measuring device has been initiated by a START signal from a time-correlated event registered in SP2. The output of the TDC, i.e., the number of time-correlated events as function of the correlation time is stored in a histogramming memory (HIS. MEM.) which then is read out by a computer (COMP.).

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