In the circuit below, I tried out an idea I had by sending the output of an OP AMP square wave generator to another OP AMP wired as a simple comparator. After reading on this site and elsewhere about 555 PWM circuits sent to a comparator, I decided to try to save on parts by using a quad OP AMP. The square wave generator was found in Mims "Engineer's Mini-Notebook" and the comparator basically comes from the LM324 datasheet. The diodes in series were added later, as I found the LED never fully turned off (I found that solution as well on this site in the 555 PWM section). The ultimate goal is to generate two variable frequency PWMs to drive two 6V 100mA (max) motors in as small a form factor as I can manage. However, this circuit does not appear to have enough power to operate a single motor. My questions are: how can I change this to drive a 6V motor? Should I go with a 555/comparator circuit instead? I'd really like to do the work myself, maybe somebody could just point me in the right direction? I'm just now beginning to understand Ohm's Law and the like, maybe someone could tell me how to calculate for this circuit.