﻿ oipapio

### Simple N-JFET circuit with PWM

I have the following N-JFET DC circuit for which I must find the output voltage \\$V_{out}\ = V_D\\$ (the drain voltage with respect to ground) when a PWM signal from \\$-10V\\$ to \\$0V\\$ is applied to gate. I can solve the circuit when the signal is at \\$-10V\\$ so I will focus exclusively on the \\$0V\\$ part.The circuit is simulated with the PWM signal at \\$0V\\$ applied to the gate of the JFET, thus explaining the connection between the gate and the source to ground.I know that \\$I_{DSS} = 10mA\\$ and the pinch-off voltage \\$V_p = -4V\\$ and I found ...Read more

### For the same JFET why are there two curves in a Transfer characteristics graph?

I am trying to learn about n-channel JFETs from David. A. Bell's book. In the transfer characteristics graph, there seem to be two curves as shown. Note that VGS(off) = VpAs you can see, one curve is drawn for the minimum values of VGS(off) and IDSS and the other curve is drawn for the maximum values of VGS(off) and IDSS. The book shows an excerpt from a data sheet and says that the manufacturer has mentioned the values of minimum and maximum of VGS(off) and IDSS and uses this formula to draw the curves:I can't understand how there can be maxim...Read more

### homework - Determine transconductance of a JFET given only voltage gain and internal drain resistance

I have a homework question as follows:If a JFET having a specified value of rd=100 kΩ has an ideal voltage gain of Av(FET) = -200,what is the value of gm ?As far as I know, the closest formula for gm relating Av and rd is Av = -gm(rd||RD)but RD is not provided in the question. I would use RD=0Ω, but that would result in 1/(1/100kΩ)+(1/0Ω), which is undefined. Is there some other way of doing this?...Read more

### Understanding p JFET

I would like to make sure that I understood p JFET (https://electronics.stackexchange.com/a/97350/78253) right:With SWitch1 in its current position, there is voltage at the gate of the J1 p JFET, the depletion layer is large, current through J1 is blocked, D1 is dark.With SWitch1 closing to the ground, there is no voltage at the gate of the J1 p JFET, the depletion layer is very small or not there at all, current can flow through J1, D1 is shining (correct voltage V1 and resistance R1 provided).Correct or what did I make wrong?...Read more

### jfet - How can I make a simple voltage-controlled attenuator?

Having discovered just how awful the AC ripple is on some of my 5VDC wall-adaptors, I decided to make an Arduino program to calculate the RMS AC component and DC component of an adaptor under varying current loads.My current issue is that the Arduino (and it's ADC's and DAC's) run on 5V, so 0-5V is it's analog input and output range. Many "5V" adaptors output a little more than that (and I want to be able to test 9V and 12V adaptors as well). So, I want a way for the Arduino to attenuate the input down to something within the 0-5V range, and th...Read more