BF862 instead of 2sk170?

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> There is a SOT-23 to pin adapter available.

We make our own. :)


Patrick
 

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I read that most of the smd jFET heat emanates from the Gate lead.

Is that correct?

This is probably correct, but there might be exceptions. On most JFETs the back side of the die is the Gate connection. On the SOT23 lead frame the die is mounted on the center pin (usually called pin 3). On bipolar transistors the Collector is the back side of the die connection.

On the Tek 576 photo Jackinnj posted it looks like there is a slight oscillation on the top curve. Since the 576 doesn't have much bandwidth (perhaps 2 MHz) the oscillation could be much bigger.
 
> If you use an SMT adapter the leads will bleed off some heat.

To where, the FR4 PCB material (poor thermal conductor) ?

For audio applications, one wishes to place a gate stopper close to the gate pin.
So the copper on which the gate pin is soldered cannot have a large are for dissipation.


Patrick
 
Boys, you should have read Juma's threads. He explained everything you are arguing about a few years ago.
First picture shows Juma's work. Gate stopper, big copper area for gate pin. If you are not fearless builders, like Papa sez, you can solder thin copper foil to make cooling area even bigger.
Second picture is my work. Looks awful, but it works.
 

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