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[metaldetector107]

Hi all
please i need equivalents for LM308 LF353 J107

thanks all

[porkluvr]

LM308 does not have many direct substitutes besides the LT1008 (from Linear Technology Corporation). If you can't find LM308/LT1008 your best choice would depend on what circuit you need it for. The combination of specifications (and custom compensation pins) is unique, so far as I know. They draw little power, and have relatively low noise. Bandwidth and supply rejection can be customized by the compensation pins. OP08 was another direct substitute, but is no longer made.

The LF353 is more easily substituted. TL072 is a very close match. TL082, AD712, LF412 are also very close.

J107 - I think it is most often used in MD circuits for the 4V cutoff voltage, making it useful in 5V systems. Some good subs might be J113, 2N4393, (and BF245A, BF245B,and TIS75 but having different pinouts).
You can generally swap the S & D conections for these JFETs with no performance difference. Locate the G pin, and the other two can be either S or D, whichever you want.

[Unregistered]

F6NA3j

If you are looking for a substitute FET to use in a Tesoro transmit circuit: the selection of FET can affect the P-P voltage, or might cause an unstable signal. There is a wide possible variation between BF245A and BF245C.

[Ultimate_Haze]

Please tell us why you think so?
I remember that the how jfet part in TX were remooved without any changes in work of device!

[ivconic]

Aside all the fet specifications... here,at this exact setup fets are used as simple switches and nothing else. So...really doesn't matter which one from the list you will use as long as you respect pin orientations.
I tested only J107 and BF245 (a and c). Havent noticed any differences so far. So...simple switch.... nothing else..

[porkluvr]

wrong, again!

So...really doesn't matter which one from the list you will use as long as you respect pin orientations.

I confess, I was "unregistered". Ivconic is right (again). I made some more tests that surprised me. With a single ended (+8V) TX supply there is practically no difference between using BF245(ABC), J107, and 2N4391,2,3. I was absolutely sure there would be some difference worth reporting.

Here's where I went wrong:
I investigate +/-5V and +/-8V transmit supplies because I have two cabinets that only accept 9V batteries -and- since I'll most likely be using a LT1615 or similar SMPS regulator, then why not pump up the output in the process...? It seemed logical.

It might require changing FET gate components, (and capacitice coupling to the phase comparators if splitting the supply) but with elevated supply voltages there is possibly a huge difference in output - depending on which FET in used. I forgot just how much I was deviating from the original circuit. I was looking at a different circuit and I appologize for the mis-information.