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Registered Member #1537
Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51
is it possible to drive a motor using a high power opamp, without all the shrapnel they say to use in the data sheet. ie just a voltage follower connected to a motor with a protection diode.
well without telling us what rating the motor is we cant do much....but that opamp can output 3A tops, so if your motor draws less than that then i dont see why not.
However youd be much better off using a MOSFET as the driver, and then just use a low power cheaper op amp to control it.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
If you look at the data sheet you'll see there's an internal diode from the output pin to the +Vs pin, so if you're going to operate in a unipolar mode (one direction only, Motor+ to +Vs) the internal diode should suffice.
Personally I'd add 2 diodes as in Figure 1 of the data sheet whether unipolar or bipolar (Fwd/Rev). Internal SOA and thermal protection should cover most other fault conditions.
Registered Member #1537
Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51
h the motor specs are quite low, i was thinking two of the small flat sided motors less than an amp i total i guess. i will be driving it bipolar, so that when the output of the opamp is positive the motor turns one way and when it is negative it turns the other way.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
When I've needed to do this in the past, I made an H-bridge with four power BJTs, driven by two regular small-signal op-amps, plus some booster transistors, as the op-amps couldn't give enough current to drive power transistors directly.
For an inductive load, two clamp diodes per output are certainly a good idea. I was driving peltiers, not motors, so I didn't need them.
Registered Member #1537
Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51
thanks allot for the offer, though in the design i am wanting to make there will be no microprocessor, it is all analogue, i amy go with a design similar to the motor controll section of this schematic. and for clarity the project as a whole will be similar to this schematic with some modifications.
Registered Member #1537
Joined: Thu Jun 12 2008, 06:44PM
Location:
Posts: 51
as far as i can see the input for that device is a 4bit binary that is internally converted to analogue to make the pwm signal, as my project does not have a microprocessor ii cannot produce the binary number necessary to drive the chip, hence any pwm ic i use will have to have a voltage controlled driving circuitry.
p.s. i did look at the data sheet before posting previously.
Registered Member #2123
Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312
Just buy a 10-position 4-bit BCD switch or a 16-position true binary switch, and use these to control the 4-bit data line. No uC or any other digital chips required.
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driving a motor with op amp
