--Apple-Mail-5-952507835 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; format=flowed On Mar 7, 2005, at 1:26 PM, Dwayne Reid wrote: > You've chosen a supply voltage such that all 4 transistors can > be driven directly by PIC pins. As such, it doesn't matter much > whether you apply the PWM to the upper or lower devices. Which reminds me. Are there any 'reference designs' for voltage-converting H-bridges using bipolar transistors out there? I was thinking this was easy, but it got to looking more complicated the more I looked at it :-( All the schematics I find use mosfets. I have the following which I THINK should work, but I don't have a high level of confidence: --Apple-Mail-5-952507835 Content-Transfer-Encoding: base64 Content-Type: image/png; x-unix-mode=0644; name="hv-hbridge.png" Content-Disposition: inline; filename=hv-hbridge.png iVBORw0KGgoAAAANSUhEUgAAAqcAAAGyCAIAAABWdPrmAAAACXBIWXMAABcSAAAXEgFnn9JSAAAc YklEQVR4nO3d25KjOBYFUJio/8Z8ueeBLpoGIYPNReKsFRM1mU7SqbZlbY4Q0L7f7wYACOB/dzcA ALiI1Af+0fd95sHkTzO/NZX5i/kNPsq3uXC7XlI4xJ+7GwA8U9d149dDjGUeWW5Qgr7v801abjAN 7OV/7/JxuNob4P1+v9+v1yv/4HKD5K9s2XL7U2UMv3LIU2Wef+1Hg8z247eZzc5rPCSZ4Qeu0HXd 9GDBst49vAJOHj5IHndYbjP9Nznf3nWdkp0aSX1gq2lyNxsmwE81/vVZq6Y/HTaYLU1YPp40Pvmp /41FvaRE4Lg+8K/HrCMbs3MWq2uPQxBSH/jXstAsMxpnNfEQ4apk+EjqAzuM+Xp7ypa5O/KFcl5S IpD6wBWmkZZMuL2ZlzllDlhjNR+wzxdV6cdr6WRW1Cd/MXkKQPJJkuvztz9+DYU+l1HrA6fIX5dm tor+8MCb7gTM5hjyj89+cdflgzauHJTu3Kh9u/sOAMRghh8AopD6ABCF1AeAKKQ+AEQh9QEgCqkP AFFIfQCIQuoDQBRSHwCikPoAEIXUB4AopD4ARCH1ASAKqQ/Uqu3bu5sAlZH6QJWGyBf8sIvUB4Ao 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(hmm. actually, I don't see how I'll get the middle level with this circuit. 0V is not the same as floating, is it. Rats.) Thanks Bill W --Apple-Mail-5-952507835 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --Apple-Mail-5-952507835--