F4 power amplifier

[Magura]

Wow, excellent report, and wonderful suggestions... so, with a hefty water cooled heatsink, I could up the bias from 200 mA to what value?

BTW, I think you're confusing 200mA for 200mV voltage drop over the source resistor.


Magura

 

[carpenter]

BTW, I think you're confusing 200mA for 200mV voltage drop over the source resistor.


Magura

You're correct, Magura. I make this mistake more often than I care to admit.

I'll have to go back and reread Ed's post.

 

[carpenter]

So, P1 adjusts the bias by increasing (or decreasing) the voltage around the source resistor, correct?

 

[Zen Mod]

So, P1 adjusts the bias by increasing (or decreasing) the voltage around the source resistor, correct?

"increasing (or decreasing) the voltage around the source resistor"


that's just consequence of bias changing , not root of

 

[carpenter]

Gotcha... but P1 adjust this voltage up and down?

 

[Magura]

Gotcha... but P1 adjust this voltage up and down?

Well, you adjust the current, the voltage drop across the source resistors is just an easy wat of measuring the current.


Magura

 

[carpenter]

Thanks

 

[Zen Mod]

Gotcha... but P1 adjust this voltage up and down?

(what you do on) water facet is responsible for amount of water flowing to the floor ........... yes

but how much your legs will be wet - really depends of fact how long your legs are......



source is gnd-ed ;

you put some voltage on drain ;

current flow through DS pipeline depends of voltage you put on gate .

all voltages respectively to gnd (source!!)

 

[carpenter]

Thanks Choky, I'm going to take a walk and chew on those tid-bits you tossed my way.

 

[carpenter]

I keep referring back to my little ZV7 project. Nelson had a 0.5ohm resistor in the CCS. He runs 3 volts across it which yields 6 amps. Is this what I do to calculate the amperage available to the FETs in the F4?

I'll be back in an hour, or so.

Time to exercise my heart...

 

[vitalstates]

now you're really making me wish I hadn't left the land of thermionics.......life was simple then, the girls were pretty, the mars bars were 6d each oh oh oh........

any way water reminds me of fish, fish remind me of flies, and flies remind me of steen with his fly open...oh choky stop it

 

[Magura]

He runs 3 volts across it which yields 6 amps. Is this what I do to calculate the amperage available to the FETs in the F4?

Yes that's simply ohms law at work


Magura

 

[Zen Mod]

now you're really making me wish I hadn't left the land of thermionics.......life was simple then, the girls were pretty, the mars bars were 6d each oh oh oh........

any way water reminds me of fish, fish remind me of flies, and flies remind me of steen with his fly open...oh choky stop it

 

[vitalstates]

wrong kind of water...thats exactly what I've got...

Hi Carpenter, sorry I missed the question before, its single ended input - single stereo amp...

try this, it seems to be well written ... http://www.kpsec.freeuk.com/voltage.htm

Regards

Ed

 

[carpenter]

I keep referring back to my little ZV7 project. Nelson had a 0.5ohm resistor in the CCS. He runs 3 volts across it which yields 6 amps. Is this what I do to calculate the amperage available to the FETs in the F4?

Yes that's simply ohms law at work


Magura

Perfect. Thanks Magura, and thanks Ed for the link.

So, with adequate heat removal, I can run 750mV bias.

750mV divided by 0.47 ohms = 1.6 amps per device.

1.6 amps times 0.47 ohms = 0.75 watts; so the stock 3 watt resistors are up to the task, correct?

Hope I'm doing this right....... shoot, amps times volts = watts. I did that last calc wrong.... should be amps squared times ohms which = 1.2 watts.

 

[Magura]

Perfect. Thanks Magura, and thanks Ed for the link.

So, with adequate heat removal, I can run 750mV bias.

750mV divided by 0.47 ohms = 1.6 amps per device.

1.6 amps times 0.47 ohms = 0.75 watts; so the stock 3 watt resistors are up to the task, correct?

Hope I'm doing this right.......

You are running 1.6A bias, the 750mV is nothing but your way of measuring it.

Not quite right, but almost there.

1.6A multiplied by 0.47 ohms = 0.75V AKA 750mV

Current times voltage = power. 1.6A multiplied 0.75V = 1.2W

Magura

 

[carpenter]

You are running 1.6A bias, the 750mV is nothing but your way of measuring it.

Not quite right, but almost there.

1.6A times by 0.47 ohms = 0.75V AKA 750mV sp current times voltage = power. 1.6A times 0.75V = 1.2W

Magura

You're quick!!

 

[Magura]

Oh, you found the error yourself while I was typing


Magura

 

[Zen Mod]

Perfect. Thanks Magura, and thanks Ed for the link.

So, with adequate heat removal, I can run 750mV bias.

750mV divided by 0.47 ohms = 1.6 amps per device.

1.6 amps times 0.47 ohms = 0.75 watts; so the stock 3 watt resistors are up to the task, correct?

Hope I'm doing this right....... shoot, amps times volts = watts. I did that last calc wrong....

P=I^2 x R

so P= 1,6^2 x 0,47= 1,2W ........... 3-watters still good

 

[carpenter]

You guys are the best!

group hug for everyone...