Irfp460 amplifier - Page 1
Forum section: electronics / rf-microwave

author: leo20k
author_rank: Newbie
timestamp: May 20, 2023, 11:57:41 am
content: I have an issue with a small RF amplifier ,the output signal is weaker than the input

author: daisizhou
author_rank: Super Contributor
timestamp: May 20, 2023, 12:09:44 pm
content: Is a transistor or MOS transistor normal?

author: leo20k
author_rank: Newbie
timestamp: May 20, 2023, 03:41:57 pm
content: I forgot to label the photos the bottom one is the amplifier the top is the RF generator

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 21, 2023, 12:12:01 am
content: Where did you get this idea from? Makes no sense at all.It has a gate capacitance of 4nF, so at 16MHz the gate has 2,5Ohm impedance.So driving the gate with 800pF will make NOTHING.You'll need a lot of energy to drive that gate, but even in that case the difference will be close to nothing, the IRF460 is not made for RF.If you want to make RF amplifier, better go with a BJT, and still, it'll be not so easy!

author: leo20k
author_rank: Newbie
timestamp: May 21, 2023, 07:57:44 am
content: I'm not very good at RF but I will try to figure it outI might use a vacuum tube instead it's a 6n3p tube but I might have some issues with it grid capacitance is 2,45 pf .From what I found it is an amplifier tube .About the irfp460 I don't know if this exact one is werd but it likes to randomly start to oscillate at 45 MHz when it is not connected to the driver.The 45 MHz signal from it is strong enough to light up a small CFL bulb.About using bjts I don't have any that can work at 16 MHz and are decently strong, the only ones that should handle the RF ar 2n2222 but it is a bit weak.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: May 21, 2023, 10:28:33 pm
content: Quote from: leo20k on May 20, 2023, 11:57:41 amWrong fet for the job. The Irfp460 is really only good for Low Frequency amps. Change to an IRF510 or IRFZ24N, they will both work adequately at 16Mhz.

author: LM21
author_rank: Regular Contributor
timestamp: May 22, 2023, 01:37:46 pm
content: As pothers have said you have a problem there. But there are fets with lower gate capacitance. Search Digikey or others. I have seen power fets with gate capacitance of about 150pF. To drive your fet, a gate driver IC would help, but 16MHz is a bit high. You could try to make resonance circuit with your gate capacitance and a coil, but coil values may be a bit low, and you may get stability problems, that is, your fet may oscillate.

author: leo20k
author_rank: Newbie
timestamp: May 22, 2023, 07:18:42 pm
content: I can buy some of these on the next trip to the radio market.These should work (they are special RF transistors).

author: LM21
author_rank: Regular Contributor
timestamp: May 22, 2023, 08:49:57 pm
content: Are they RF fets, other RF transistors are also difficult to use. They are made about 20 years ago, so they may be ordinary RF transistors. I can't find any info about them.

author: richard.cs
author_rank: Super Contributor
timestamp: May 26, 2023, 08:08:08 am
content: Be warned RF transistors with pink ceramic are probably beryllia. If you end up buying them, handle them carefully to avoid chipping or breaking the ceramic and wash your hands well after handling.

author: leo20k
author_rank: Newbie
timestamp: September 13, 2023, 03:11:39 pm
content: So I found som кт930б RF transistors and it means the project is started again