Why so many devices used 9V input?
Acutally for 5V circuits, designers only need 7.5V input for 5V regulator such as LM7805.
If used 9V, the voltage regulator becomes hot and wastes a lot of energy if the device is running continuously.
Many 9 volt DC sources are unregulated and have large ripple voltages riding on the average DC. They also should work with the line voltage in a brown out condition. The higher the unregulated supply, the lower the line voltage can be and still have the linear regulator fed with at least 7.5 volts.
-- John Popelish
i thought it was used as a quark modulated accelerator?
The apparent excess voltage is used to run the Flux Capacitor tracking device that the Trilateral Commission secretly requires to be instal lld
67hophczzNO CARRIER
-- Rich Webb Norfolk, VA
Nope, far too complicated, its maximum price for minimum power
martin
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