dummy load does not draw all current

[kind2011]

i have made a dummy load specs 10a 19v  with 6x parallel mosfets, dac,  op amp and push pull driver for mosfets,  something is wrong, when i set to 6amps and connect to a supply of 5v its draw 4.1a when increasing supply from 7v to 19v it draws constant 6amps  that is fine  but below 7v the currents drops, at first i guessed that was the supply source impedance , then i connect two 1ohm 100w in parallel equals .5ohm to the supply to test and draw 7.4amps at 4.6vsupply gives 0.621ohms so the supply impedance is not the problem,
 i do not know whats going on here
thanks in advance

[EntropyWizard]

It would help to see a schematic, check your Vgs and the voltage drop on your sense resistor(s).

[kind2011]

vgs 9.4v  and vsense 2.6v and rsense 500milliohms vsupply 5.1v still gives 4.2amps im confused

schematic attached.

[dom0]

I, too, am confused by that schematic.

[wraper]

What a mess, I'd be ashamed to post something like this frankly, and would spent some time to tidy the looks of it.

[kind2011]

the first op amp (tl072) scales the input 0 to 5v , -1 to 6v , -1 when 0 to full turn off mosfet  its plus pin is connected to 5v to full to output 6v that goes to  the second op amp that is the voltage follower the two transistor are actually tip122 and tip127, this two takes the output from second op amp and provides more current to gates of mosfets the resistor between base and emitter is to starts giving current to gates of mosfets its what i read somewhere, the 500milliohms is the sense resistor

simulated results gives more aproximated output 9amps
sorry for the mess

[kind2011]

sorry for the mess here is a more clear schematic

[kind2011]

more my english is not my native language

[dmills]

T2 looks very, very wrong to me.

Regards, Dan.

[moffy]

The chances of the MOSFETs oscillating without gate degenerating/series resistors near to each gate is very high.

[Christopher]

Much better way to do it is to have a opamp&sense resistor per mosfet,

also 100ohm resistor between opamp output and gate, forget the push pull driver, as this can cause problems

i see no high frequency decoupling for the opamp, something like 200pF between the current sense input and output