Re: Why use a transistor to drive a motor?
Martin Cote <mentalray@xxxxxxxxxxxx> writes:
Since the motor seems to require 470mA to run,
Which is enough to fry most logic circuits. The transistor lets a
small current (2.15 mA) control a larger current (470 mA) in cases
where the control current is simply not powerful enough.
Most TTL/CMOS outputs are only rated for a few milliamps.
The "hfe" spec is the amplification factor - in this case, 300 means
that a 470mA load needs (470/300 = ) at least 1.57 mA of input
current. At 2.15 mA input, the load can draw up to 645 mA.
Approximately. Good to leave some margin too.
.
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