Tag: Free Book on Semiconductors
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6.2 Depletion-type IGFETs
Insulated gate field-effect transistors are unipolar devices just like JFETs: that is, the controlled current does not have to cross a PN junction. There is a PN junction inside the transistor, but its only purpose is to provide that nonconducting depletion region which is used to restrict current through the channel. Schematic Symbol and Physical…
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6.1 Introduction to Insulated-gate Field-effect Transistors
As was stated in the last chapter, there is more than one type of field-effect transistor. The junction field-effect transistor, or JFET, uses voltage applied across a reverse-biased PN junction to control the width of that junction’s depletion region, which then controls the conductivity of a semiconductor channel through which the controlled current moves. Another…
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5.4 Active-mode Operation (JFET)
JFETs, like bipolar transistors, are able to “throttle” current in a mode between cutoff and saturation called the active mode. To better understand JFET operation, let’s set up a SPICE simulation similar to the one used to explore basic bipolar transistor function: Spice Simulation of a JFET Operation jfet simulation vin 0 1 dc 1…
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5.3 Meter Check of a Transistor (JFET)
Testing a JFET with a multimeter might seem to be a relatively easy task, seeing as how it has only one PN junction to test: either measured between gate and source, or between gate and drain. Testing Continuity of an N-channel JFET Testing continuity through the drain-source channel is another matter, though. Remember from the…
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5.2 The Junction Field-effect Transistor (JFET) as a Switch
Like its bipolar cousin, the field-effect transistor may be used as an on/off switch controlling electrical power to a load. Let’s begin our investigation of the JFET as a switch with our familiar switch/lamp circuit: Remembering that the controlled current in a JFET flows between source and drain, we substitute the source and drain connections…
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5.1 Introduction to Junction Field-effect Transistors (JFET)
A transistor is a linear semiconductor device that controls current with the application of a lower-power electrical signal. Transistors may be roughly grouped into two major divisions: bipolar and field-effect. In the last chapter, we studied bipolar transistors, which utilize a small current to control a large current. In this chapter, we’ll introduce the general…
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4.16 BJT Quirks
An ideal transistor would show 0% distortion in amplifying a signal. Its gain would extend to all frequencies. It would control hundreds of amperes of current, at hundreds of degrees C. In practice, available devices show distortion. Amplification is limited at the high frequency end of the spectrum. Real parts only handle tens of amperes…