Here is an untested circuit. It should work. Might need some tweeking and bypass caps.
Dean Cooper
dclabseng.comhttp://files.engineering.com/getfile.aspx?folder=21e6b521-f3a5-44e6-9178-338e17ab7add&file=DCLabs_freebie.pdf
Match the impedence at the inverting and noninverting inputs at U1B by making the capacitor at U1B+ 220nf and the parallel combination of the 2 resistors at that node equal to 10K. Then use a lower value pot to set current. This will minimize your offsett problem.
The lower the value you can...
The rise and fall times of the MOSFET have more to do with the gate to source capacitance and gate resistor than the tr/tf of the driver.
Most drivers switch in the nS range.
IRS2117 Tr/Tf 75-135 ns
HIP2101 Tr/Tf 10nS w/ Cl = 1000pf
Dean Cooper
dclabseng.com
Thomaslt,
I am with Benta. Go with a driver. The IRS2117 you mentioned would work with IRZ44 N channel MOSFET. You will need an VCC less that 25V though.
Dean Cooper
dclabseng.com
Orcad is notorious for wrong pinouts on their library parts. I have been burned a few times. You can change the pin number in either layout or capture. I prefer capture.
Procedure to edit part:
1. Select part in Capture.
2. Right click and select edit part.
3. Select pin you want to change. A...
Use Madcow's suggestion (lm5118) or similiar IC. The LM5118 circuit would fit on a small pcb. Mount the circuit board vertically with SIP8 pin spacing. You might have some mechanical issues to deal with, but this would meet your specifications. I did something smiliar to this when replacing a 3...
Use an IRFZ44 MOSFET (International Rectifier) and HIP2101 driver (Intersil). Heatsink the Mosfet as it will dissipate around 3 watts at 50% duty cycle. I assume the pressure is variable per the 0 to 100% duty cycle spec. I am little confused why you would vary the output voltage. Why not...
