economical motor driving circuit - saves components and energy

saves components and energy Oh, for the good old days, when if you wanted to run a motor for two minutes you switched on the power for two minutes. Now we have computer-controlled robot arms, elec- tronic mice, and all manner of technological advances. For all this, however, many people still shy away from the idea of something like a motor-driving circuit. As the drawing here shows, such a circuit is quite straightforward, especially as we have even gone so far as to design a printed circuit board for it. The circuit has two inputs and if both are "1" (+12 V) nothing hap- pens. As soon as the voltage on one of the inputs, A, for example, becomes zero driver transistor T5 conducts. This causes both T1 and T4 to conduct and the motor turns in a particular direction. This brings us to the stage where we must ex- plain why the circuit is "economical". It will not have escaped your notice that each pair of transistors in the bridge is controlled by a single driver transistor. This not...