Replacement for SRF3999 RF power MOSFET?

'SRF' are propritary part numbers, custom marked for their customer. BTW, Motorola is no longer in that business. On Semiconducotr took over those lines years ago.

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Michael A. Terrell
Central Florida

Hi Yes I do know that, but all SRFs was common commercial transistors and I do remember that there was a list available with the equivalent, back at 80's. I had such lists, but after 3 lab moves many papers have been lost ;( So anyone knowing what was the SRF3999 on a commercial available P/N? Thanks in advance Sotiris

PS These were used at 150W P-P RF amplifiers to HARRIS FM transmitters, if that helps to wake up memories ;)

On Thu, 15 Nov 2007 12:25:16 -0800 (PST), pdmtr put finger to keyboard and composed:

I have a 1984 Motorola master selection guide. The only RF Power FETs with a 150W power spec are MRF140 and MRF150. MRF174 is rated for

125W. The first two are characterised at 30MHz, the latter at 150MHz. All but the MRF150 (50V) have a Vdd of 28V. The case style is 211-11 (0.500 flange).

- Franc Zabkar

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Hi Frank Thanks for the suggestions but these are case style 316-01 (more like the MRF317 transistors), working at 28Vdc (although the PSU can be adjusted up to 32Vdc !? ). I do have all of the Databooks from Moto since late 70's until even after the name turn to "ON semic" (at first, now at Macom & Freescale) and have tried to find similarity to RF MOSFETs for them, without any luck! The original HARRIS transmitter circuit schematic has them as MOSFETs, but I'm a bit sceptical about them, as the topology, connections and the circuit itself, seems to have been designed for common RF transistors... ie no +Vg bias circuit, just a 10 Ohm grounded resistor from the gates! Probably class C circuit, but I can't remember any Moto's MOSFET having that case style (316-01 6lead flange planar)! Thought to ask here as there was times that an SRF to MRF chart published periodically from Moto, and maybe someone still have them to give a look... :( I might try to put the MRF317 ! instead of some MOSFETs as the RF output power levels, PSU and the onboard broadband transmittion line input/output matching section looks quite similar (if not say as exactly same) with those used with the MRF317s! However thanks everyone replied to my quote... Regards Sotiris

On Nov 16, 11:49 pm, Franc Zabkar wrote:

text -

This is an old post, but I have some original new old stock SRF-3999, just found in grandfathers supply.

Then email the guy.

He's not here, and chances are good he was never here longer than to post this.

CHances are good that the email address on the post isn't any good anymore, but that makes more sense than posting a reply 6.5 years later.

Just because google allows replies to messages older than 30 days doesn't mean there is any reason for replies to posts older than 30 days.

Michael