power amplifier with lm675 -  please help me

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi!
I'm trying to aplify the power so that the supply power can turn/ drive my motor using LM675 as in the first page of this datasheet:
http://www.national.com/ds/LM/LM675.pdf

I just replaced the RL with my motor, but how can I:

  1. Set up the gain of the power amplifier? Is it by changing only the 20k resistor?
  2. How can I know/ verify what is the power amplifier gain without having to measure the voltage & current?
  3. How to limit/reduce the amplified power so that it is not excessive or will not damage my motor?
  4. I'm trying to make the motor turn both cw and ccw, but after implementing this amplifier, it only turns cw. How can I make it turn in both direction?
    Sorry if my questions sound stupid/ very basic.
    Thanks
2

Did you try hooking it up like it shows on page 8?
To turn the motor in both directions, you need the current to go in both directions.
For that, an H bridge may be more useful - hard to say without more info on your motor.
You have no measuring capability at all?
If you look up Op amp circuits on google, there are many sites that can tell how to calculate a circuits gain. If you search for application notes on that particular amp you may be able to find things also.