![]() ![]() However, solid-state analogue switches are not ideal as there is always some loss associated with the conducting channel due to its resistive value when ON. The Ideal SwitchĪn ideal analogue switch would create a short-circuit condition when closed and an open-circuit condition when open, in a similar fashion to a mechanical switch. Also, since the eMOSFET is used mainly as a switching device, it generally operates between its cut-off and saturation regions thus V GS acts as an ON/OFF control voltage for the MOSFET. Note that a MOSFETs Threshold Voltage, V T is the minimum voltage applied to the gate terminal for the main channel between the drain and source terminals to start conducting. An N-channel MOSFET behaves like an open switch when the gate-source voltage, V GS is less than the threshold voltage, V T.An N-channel MOSFET behaves like an closed switch when the gate-source voltage, V GS is greater than the threshold voltage, V T.Then we can see that for the n-channel (NMOS) and p-channel (PMOS) enhancement MOSFET to operate as an open (OFF) or closed (ON) device the following conditions must be true: The main advantages of MOSFET, or metal-oxide-semiconductor FET, technology over bipolar devices is that its gate terminal is insulated from the main conducting channel by a thin layer of metal oxide, and the main MOSFET channel used for switching is purely resistive.Ĭonsider the basic N-channel and P-channel enhancement MOSFET (eMOSFET) configurations below. The MOSFET as an Analogue Switchīoth Bipolar Junction Transistors (BJTs) and Field Effect Transistors (FETs) can be used as a single-pole electronic switch in a wide variety of different applications. But first lets consider the operation of a Field Effect Transistor, or FET as a basic analogue switch. The type of solid-state switch which allows for a signal or data transfer in both directions is called a Transmission Gate, or TG. ![]() ![]() CMOS devices where both NMOS and PMOS transistors are fabricated into the same gate circuit, can pass (closed-condition) or block (open-condition) an analogue or digital signal, depending on the digital logic level that controls it. MOS technology uses both NMOS and PMOS devices to perform the logical switching functions, thus allowing a digital computer or logic circuit to control the operation of these analogue switches. The obvious choice is to use much faster acting solid state electronic switches which use metal oxide semiconductor (MOS) analogue gates to route the signal currents from their input to their output, with the well-known CMOS 4016B bilateral switch being the most common example. The switching and routing of digital and analogue signals (both voltage and current) can easily be done using mechanical relays and their contacts, but these can be slow and costly. For example, single or dual normally open (NO) or normally closed (NC), single-pole single-throw (SPST), single-pole, double-throw (SPDT) configurations etc, in much the same way as for conventional electromechanical relays and contacts. ![]() The open and closed operations of the switch positions are usually controlled by some digital logic network, with standard analogue switches available in many styles and configurations. The analogue switch is a solid-state semiconductor switch that controls the transmission path of analogue signals. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |