The Thermistor Fan Control Circuit is working very well for my PA47 RF Power Amplifier (see selected links to previous posts). The PCB was re-laid out to include the circuit. Initially for testing, I just used an available 10K NTC Thermistor super-glued to the heatsink on a 1 Watt PA47 configuration.
For this project, my plan is to attach a small 10K NTC 0402 size thermistor directly to the 2N7000 for best FAN Control and cooling of the FET.
Here are some Microscope photos of the attachment process.
Shown is the 0402 Thermistor super-glued to the back of the TO-92 2N7000, along with the tip of a standard X-Acto Blade (for additional size reference).
|Attached 0402 Thermistor on a TO-92 2N7000|
|Thermistor with Wires Attached|
|Waiting for the Epoxy to Cure|
I am not sure of the thermal conductivity of Hobby Epoxy, perhaps something else would be better? Maybe another harder Epoxy such as JB-Weld?
This is ALL probably not necessary, but I wanted to see if I could do it. For future projects and use of Thermistors will probably be a larger size, and maybe not attached directly to the FET.