The possibility of creating a universal analog-to-digital multiplexer-demultiplexer is shown.
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As is known, a multiplexer and a demultiplexer is an electronic device designed for selective signal transmission from one of several inputs to one output, or, on the contrary, signal transmission from one input to one of several outputs. Channel switching is performed by digital signals supplied to the control inputs.
First, let’s consider the operation of a control node containing key elements controlled by digital input signals. Figure 1 shows an example of such a node based on discrete elements such as bipolar or field-effect transistors; or using two “NOT” logic elements. When applying to the input (Inp) of such a node, signals of the level “Log. 1»/«Log. 0” the output signal levels Out1 and Out2 are switched. To switch, for example, four channels, it is necessary to use two similar control nodes.
Figure 1 Control node using discrete elements such as bipolar or field-effect transistors.
Figure 2 shows the electrical circuit of the signal transmission channel switching unit, made using two control units, Figure 1, as well as diode-resistive elements. The signals from the ABCD outputs are sent to the corresponding ABCD control inputs of analog switches, Figure 2.
Figure 2 Electrical diagram of the analog switch control unit using discrete elements.
When digital signals of the level “Log. 1” or “Log. 0” are applied to the inputs, X1 and/or X2 of the control nodes implements four combinations of selective appearance at the outputs of the ABCD levels “Log. 1”. The inputs and outputs of analog switches have the property of reversibility, which allows the device to be used both as a multiplexer and a demultiplexer.
Figure 3 shows a variant of the control unit for analog switches from a set of logic elements “NOT” and “2AND”.
Figures 3 Electrical diagram of the analog switch control unit using logic elements.
To be able to disable the passage of any signals from the input to the output of the device, or vice versa, the scheme shown in Figure 2 can be supplemented with the function of general disconnection of the passage of signals, Figure 4. When an Inhibit signal of the “Log. 1” level is applied to the input, the transistor Q opens and shunts the control inputs of the analog switches ABCD through the diodes.
Figures 4 Electrical diagram of the device for general disconnection of signals passing through all switching channels.
Figure 5 shows the possible pin arrangement of the universal analog multiplexer/demultiplexer chip, its schematic representation, and truth table.
Figure 5 Possible pin layout of the universal analog multiplexer/demultiplexer chip, its schematic representation, and the truth table.
Figure 6 demonstrates the possibility of using such a device as a multiplexer when signals from 4 sources are fed to the ABCD inputs. When digital control signals are applied to inputs X1 and X2, one of the signals taken from sources E1–E4 will pass to the output Y of the device.
Figure 6 Using a universal analog multiplexer/demultiplexer as a multiplexer, its graphical designation, equivalent circuit, and truth table.
Figure 7 shows the options for using a universal analog of a universal multiplexer/demultiplexer as a demultiplexer.
Figure 7 Using a universal analog multiplexer/demultiplexer as a demultiplexer, its graphical designation, equivalent circuit, and truth table.
Figure 8 shows an example of using a device for selectively enabling/disabling information transmission channels from sources E1–E4 to the outputs/inputs of ABCD.
Figure 8 Examples of using a universal analog multiplexer/demultiplexer to control the passage of signals through one of the channels involved.
The described device can be used for switching both analog and digital signals of positive polarity, however, with a slight improvement of the device, it can be converted to switch signals of both positive and negative polarity.
Michael A. Shustov is a doctor of technical sciences, candidate of chemical sciences and the author of over 800 printed works in the field of electronics, chemistry, physics, geology, medicine, and history.
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