PH4705/ET4305: Analogue Multiplexer An Analogue Multiplexer is simply a switch that connects multiple analogue inputs signals to a single output one at a time. It is used to concentrate analogue inputs into a single information stream for further processing, either because the analogue inputs change only slowly so need not be continuously monitored, or because the following processing is complex and the expense of a processor for each signal cannot be justified. Analogue multiplexers use FETs as switches and which input is connected to the output is usually determined by a digital address word. Typical IC devices have either 8 or 16 inputs.
PH4705/ET4305: Analogue Multiplexer IC analogue multiplexers come in two variants. For single ended or differential inputs (matching our two types of sensor circuit). The device shown is DG406 single ended and DG407 differential. Note the addressing a enable logic.
PH4705/ET4305: Analogue Multiplexer Another common IC is the DG408/409 with either 8 single ended or 4 differential inputs. Channel on-resistance: 100Ωmax, leakage (when off): 5nAmax, channel characteristics closely matched. Digital input TTL/CMOS compatible, Power supply ±18v max (dual or single, input voltage range- rail to rail, Low power 1.25mW max.
PH4705/ET4305: Analogue Multiplexer A typical application of an analogue multiplexer, gathering multiple analogue signals through a sample and hold and an analogue to digital converter into a digital data stream.
PH4705/ET4305: Analogue Multiplexer This is the circuit of a single channel of an analgue multiplexer showing the switching devices (MOSFETs) and the associated control, a complex and sophisticated circuit that can’t be emulated with discrete devices.