I paid someone to design this amp a fiver, is it any good?

Thread Starter

CosmicOrderMachines

Joined Oct 31, 2019
28
Update: I need help
Since this gig started a week ago the money is already being held by fiverr. The money will be given to the seller in 3 days if I don't dispute and win for this shit design. We are in the second stages because I did dispute based on what you guys were saying. And that worked. This idiot "revised" his circuit. Now I need to know if there is any reason I should be paying for this or if you guys can find flaws that can downright destroy this whole deal.

LTspice file attached below
Here is the new schematic
Comments I have so far, "3055 will not function at 1 MHz. Its gain-bandwidth product is 2.5 MHz, and it needs to provide a current gain of at least 20, which it can not." , "the first time the amplifier output goes below GND, D4 will burn up"
I should also note the goal of this was a 140watt amplifier for 500khz-1Mhz.
schem_circuit_revised.PNG
You guys were great. Hope you don't mind me pinging you. I have some serious thanks after this. @jpanhalt , @OBW0549 , @AlbertHall , @MrAl , @Sensacell , @AnalogKid


Hi,

This amp is 140 watts between 500khz and 1Mhz for my signal gen. I paid this person on fiverr and am wondering if this thing is any good before I accept the delivery


schem_circuit.PNG

UPDATE: My fiver guy said Q5 is supposed to be a 2N3019 like Q3. Thanks to @bertus for pointing that out
 

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AlbertHall

Joined Jun 4, 2014
9,626
Color me stupid but what is the circuitry doing after the fuse?
It has an input (the output of the amplifier) but it has no output so it can have no function.

Maximum collector-emitter voltage for the 2N3055 is 70V. When the output is close to either supply rail (±55V) there will be approaching 110V across one of them.

Does R4 represent the output load, or is the actual load to be connected in parallel with this resistor?
 

Thread Starter

CosmicOrderMachines

Joined Oct 31, 2019
28
It has an input (the output of the amplifier) but it has no output so it can have no function.

Maximum collector-emitter voltage for the 2N3055 is 70V. When the output is close to either supply rail (±55V) there will be approaching 110V across one of them.

Does R4 represent the output load, or is the actual load to be connected in parallel with this resistor?
Actual load is to be connected in parallel with this resistor.

I will bring up the 110 across them to my fiverr guy. See what he says.
 

OBW0549

Joined Mar 2, 2015
3,300
Well I was hoping I would not get one of these responses. No I did not pay. Can you give me any slight details and I can relay it back to the guy, maybe get it fixed
There is so much wrong with that design-- HORRIBLY wrong-- that trying to fix it would be a waste of time.

UPDATE: My fiver guy said Q5 is supposed to be a 2N3019
Then your fiver guy doesn't know what he's doing and isn't competent to design this kind of equipment.

Drop him and get someone who isn't a total noob.
 

MrAl

Joined Jun 17, 2014
7,466
Hi,

Oh this is an amplifier? I thought it was an electric frying pan (chuckle).

Simply ask "your guy" what each part does. Then also ask how he controls the quiescent current between Q5 and Q3.
 
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