another power amplifier- lm675 questions

[nza0104]

Hi!

I'm constructing the "Non-inverting amplifier" in page 1 of the attached datasheet. In my circuit I replace the 20k ohm resistor with a 1k ohm resistor since I actually need a voltage gain of 2.
1. If the motor is set to turn forward, the voltage gain is correct, but if I set the motor to turn backward/ reverse, I do not get the correct voltage gain. What is my mistake? From my observation, if I increase the current from my power supply (I use +-8V), it will also affect the voltage gain. What is the correct current that I should set at my power supply unit?
2. I have two motors whose power needed to be amplified. I am using 2 units of LM675. I have only one set of power supply unit, so I just connect the first LM675's pin5 to the second LM675's pin5 and then to the VCC. Then I also connect the first LM675's pin3 to the second LM675's pin3 and then to the VCC. Is this right? I do not get the correct voltage gain with this connection. What is the correct way of connecting the amplifiers, since I only have one set of power supply unit?
3. What is the effect of 0.1mircroF capacitors at VCC and VEE? Is it ok not to use any capacitors at all at VCC and VEE?

Thanks.

 

[shrtrnd]

The data sheet did not attach.

 

[nza0104]

sorry 4 that.

the datasheet can also be found here http://www.national.com/ds/LM/LM675.pdf

 

[davenn]

ok its about time we saw the exact ccts you are using.
Draw out your cct showing the motor connections etc

the 0.1uF caps are for high freq noise bypassing on the power supply rails

Dave