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Saturday, November 15, 2008

Amplifier for 80 Meter Rig

Here's the LTSpice schematic for an amplifier chain that I've been building. (It might be hard to see, but maybe you can download it and look at a larger version.) Four stages, all feedback amps. The first three are class A, the final is Class AB. About 45 db total power gain -- it takes the .0001 watt (peak) from my balanced modulator and amplifies it to about 3.2 watts.

So far it seems very stable. Notice that I don't have any decoupling networks on the first three stages (other than a .1 uF cap to ground on the +13V supply rail. I tried to continue without decoupling on the final, but I got instability, so I added a 10 uH RF choke and a cap to ground as a decoupling network to the final stage. Instability disappeared. Do I need more decoupling on the other three stages?

The last two transistors are disgnated at 2N3053 and 2SC2075. That's what I'm actually using, but I haven't figured out how to get these parts into LTSpice, so I'm actually using 2N2222 models in my simulation.

Here is the actual LTSpice file: Bill's Kickpanel amplifiers

I'll talk about this project on SolderSmoke tomorrow. Comments welcome.

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Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column