So here's a bad idea. In fact, a double-bad idea.
The all-plastic TO-220 transistor package has a layer of that black silicone plastic covering the metal tab that's normally exposed on the familiar TO-220 transistor package.
It's meant to reduce assembly labor by eliminating the need for an isulating washer. The plastic body insulates it from the heat sink. You just bolt it down with a layer of compund underneath.
Sounds good. You'll find nine-volt regulator transistors in RCI-made radios using this package.
Just one problem. That layer of plastic insulation does NOT carry heat energy like a metal surface. As a result, a transistor, or 3-terminal regulator made this way CAN'T push the same amount of heat into a heat sink. No big deal for a low-power circuit like that 9-Volt regulator.
Not so swift for final transistors. Reduces the effective wattage rating in a big way.
But that's only half the story with these two finals we pulled from a Magnum S9 after they blew out. The part number appears to start with the letter "P". Try as you might, this number you see won't come up in any component-spec database.
Not so different from the missing "2S" prefix that makes the markings on a 2SC1969 read "C1969". You're supposed to know to add that "2S" before looking it up.
This part is an FQP13N10LF. You're supposed to know the "FQ" goes in front of it. Go figure. Part numbers have gotten too long to fit on a part this size, I suppose.
But the real issue is the letter "L" in the suffix. This tells you that this MOSFET is what they call the "logic" version. The gate voltage needed to turn it on is just over half of what the normal version requires. The data sheet says the V(th), or turn-on threshold voltage will be around 2 Volts, rather than the normal 3 and a half for the standard version of this part.
I won't claim to know what difference this makes as an RF amplifier. Haven't made a proper comparison between the "L" version and the stock version. The IRF520 is also sold in a "logic" version. Called the "IRL520".
Haven't tried those as a final yet, either. If you want to try that version of a MOSFET, just be sure to turn down the gate-bias trimpot below 2 Volts before you key the mike. The normal 3.5-Volt (or so) setting will slam the thing first time you key it.
73
The all-plastic TO-220 transistor package has a layer of that black silicone plastic covering the metal tab that's normally exposed on the familiar TO-220 transistor package.
It's meant to reduce assembly labor by eliminating the need for an isulating washer. The plastic body insulates it from the heat sink. You just bolt it down with a layer of compund underneath.
Sounds good. You'll find nine-volt regulator transistors in RCI-made radios using this package.
Just one problem. That layer of plastic insulation does NOT carry heat energy like a metal surface. As a result, a transistor, or 3-terminal regulator made this way CAN'T push the same amount of heat into a heat sink. No big deal for a low-power circuit like that 9-Volt regulator.
Not so swift for final transistors. Reduces the effective wattage rating in a big way.
But that's only half the story with these two finals we pulled from a Magnum S9 after they blew out. The part number appears to start with the letter "P". Try as you might, this number you see won't come up in any component-spec database.
Not so different from the missing "2S" prefix that makes the markings on a 2SC1969 read "C1969". You're supposed to know to add that "2S" before looking it up.
This part is an FQP13N10LF. You're supposed to know the "FQ" goes in front of it. Go figure. Part numbers have gotten too long to fit on a part this size, I suppose.
But the real issue is the letter "L" in the suffix. This tells you that this MOSFET is what they call the "logic" version. The gate voltage needed to turn it on is just over half of what the normal version requires. The data sheet says the V(th), or turn-on threshold voltage will be around 2 Volts, rather than the normal 3 and a half for the standard version of this part.
I won't claim to know what difference this makes as an RF amplifier. Haven't made a proper comparison between the "L" version and the stock version. The IRF520 is also sold in a "logic" version. Called the "IRL520".
Haven't tried those as a final yet, either. If you want to try that version of a MOSFET, just be sure to turn down the gate-bias trimpot below 2 Volts before you key the mike. The normal 3.5-Volt (or so) setting will slam the thing first time you key it.
73
