Junction Field Effect Transistor - A transistor whose channel is modulated by the application of an electric field that is the depletion region of a reversed biased diode that forms the gate electrode. Characteristic features of the device are low noise and low gate capacitance.
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102 views
Bipolar Op Amp w/ Near Zero Offset?
My understanding is that if source resistance is low, a bipolar op amp has 10dB less noise than a JFET. I prefer the JFET op amps because the input offset is so low that you can eliminate coupling ...
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2answers
137 views
N-channel jfet fixed bias with high gain = 200
simulate this circuit – Schematic created using CircuitLab
I would like to know if it is possible to produce an n-channel jfet connected in fixed bias configuration with a high gain of ...
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1answer
71 views
Turning the PN junction of JFET on?
I am going to use a N channel JFET as a normally-ON switch. I am wondering if it would cause any problem in the long term reliability having the PN junction forward-biased. In other words, would it be ...
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1answer
85 views
Depletion region in JFET transistor?
In this diagram of JFET transistor the depletion region is narrower at one end and wider at other end. Why is that so? Is it due to the voltages applied at gate and drain?
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1answer
94 views
Fet is named field effect transistor,why?
Fet is named field effect transistor transistor while field effect is also producing in bjt. What are the factors/reasons that Fet is called field effect while bjt is not? I have read textbook but it ...
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2answers
78 views
odd JFET configuration
I was looking at figure 33 of the OP77 datasheet, and the JFET labeled D2 has an odd connection. Based on the way the circuit works that JFET must be a diode right? So why is the JFET connected as it ...
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4answers
358 views
Why JFET is called voltage controlled device while BJT is called current controlled device?
My question is why JFET/FET is called voltage controlled device while BJT is called current controlled as both required voltage to operate properly.In both electric field is produced so why is the ...
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2answers
362 views
Why are JFET transistors used in circuits with high input impedances?
I read an introductory textbook to understand this but it doesn't tell the reason behind it. Is that because the JFETs require much less voltage to operate comparing to BJTs and one needs to drop ...
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1answer
383 views
Is pinch off voltage of JFET constant?
The drain current is related to gate to source voltage by the following equation:
\$I_d = I_{dss} (1 - \frac{V_{gs}}{V_p})^2\$
Now, with changing \$V_{gs}\$, I think \$V_p\$ also changes. I am ...
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2answers
2k views
How to do a simple overcurrent protection/circuit breaker circuit for 12V 1-2A?
We're developing an I/O shield for Arduino (sort of) and having four FET controlled output connectors with approximated 12V 1-2A load each. I need all these four outputs to be short-circuit protected ...
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1answer
184 views
About JFET polarity
I often see the internal schema of a JFET transistor and it always look symmetrical. N-type channel that connect the drain and the source and P-type semiconductor on the gate for a N-JFET. I know that ...
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2answers
476 views
What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?
For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the ...
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1answer
542 views
What's the 2N3904 / 2N3906 FET equivalent?
Is there a generic low-power switching FET that's multiply sourced, generally readily available, most simulators already have models for, etc.?
I'm not looking for FETs that have similar electrical ...
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3answers
2k views
I don't quite understand this FET-BJT preamp circuit
I see this circuit a lot on electret microphone preamps, but I don't quite understand it. The FET is operated as a common source amplifier, so it has gain, inverts, and has relatively high output ...
