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34231Re: [beam] H_Bridge

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  • Mark Hillier
    Mar 3, 2003
      > Hi Mark;
      >
      > Mark Hillier wrote:
      > >
      > > > Hi,
      > > > Does anyone know which transistors(readyly available)
      > > > to use in a standard H-bridge configuration to drive
      > > > 12v, 2amp motors?
      > > > Any idea about FZT605,705 OR BCV27,26 Darlignton
      > > > Pairs?
      > >
      > > How about the L298N ?
      >
      > I have never liked this part.
      > OK, it has it's uses. I have used it.
      >
      > My basic problem with the L298 and others like it
      > is the poor efficiency. It uses emitter follower
      > transistors on the high side. This about guarantees
      > that there will be 3 volts or more across the high
      > side transistors.

      Agreed. The L298 has poor efficiency, but in many cases it isn't a
      huge issue. It *is* farily compact and inexpensive, which is nice.

      > This is why the Tilden and other bipolar H-bridges
      > are so favored as they have complementary transistors
      > with much higher efficiency.
      >
      > With frustration with the L298 I looked for a better
      > H-bridge. I came up with this circuit:
      > http://www.redrok.com/actuator.htm#act01
      > OK, it has some warts, but works well if high switching
      > speeds are not needed.
      >
      > I presented the design to our legal department and
      > we decided to patent it. It's still pending.
      >
      > Also, the LMD18200 with its internal MOSFET gate
      > drive charge pump works much better than the L298.

      True, but these will handle only a single motor each and they are
      something like triple the cost per unit. If you consider that you need
      tow of them to equal the function the cost of a single L298, then it's
      SIX times more expensive !

      Mark Hillier
      President, HVW Technologies Inc.
      Mark@...
      Tel:(403)730-8603 Fax:(403)730-8903
      http://www.HVWTech.com
      Development Tools for Embedded Design
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