Hello,
As part of the project I am working on, I need to use a microcontroller to control 6 small motors. The microcontroller I am using is the PIC16F819, and it can output 25mA maximum at 3.3V (when sourcing current, that is). The motors use 120mA @ 2.6V. Therefore, the output current from the microcontroller needs to be increased: I need a transistor array, one transistor per motor.
The transistor array I was planning to use is the uln2003a, from texas instruments. This is a series of 7 npn darlington pairs, with the collectors connected to the load being controlled, and the emittors connected to ground (battery negative).
My question is, what happens when the base voltage (3.3V) is higher than the collector voltage (close to zero, because it's after the load, not before it)? Will it hurt the transistors? Do I need to put a resistor in each signal between the microcontroller and the transistor array? I have actually planed on doing this, but if I can get away with just one resistor between the uln2003a and ground, that would advantageous in my situation.
I realise that NPN transistors are 'source' transistors (conduct when high voltage is applied to base), but nowhere can I find what happens when you 'super-source' a transistor.
Any ideas?
And in advance, I want to say thank you very much for any assistance you give. It's greatly appreciated!
As part of the project I am working on, I need to use a microcontroller to control 6 small motors. The microcontroller I am using is the PIC16F819, and it can output 25mA maximum at 3.3V (when sourcing current, that is). The motors use 120mA @ 2.6V. Therefore, the output current from the microcontroller needs to be increased: I need a transistor array, one transistor per motor.
The transistor array I was planning to use is the uln2003a, from texas instruments. This is a series of 7 npn darlington pairs, with the collectors connected to the load being controlled, and the emittors connected to ground (battery negative).
My question is, what happens when the base voltage (3.3V) is higher than the collector voltage (close to zero, because it's after the load, not before it)? Will it hurt the transistors? Do I need to put a resistor in each signal between the microcontroller and the transistor array? I have actually planed on doing this, but if I can get away with just one resistor between the uln2003a and ground, that would advantageous in my situation.
I realise that NPN transistors are 'source' transistors (conduct when high voltage is applied to base), but nowhere can I find what happens when you 'super-source' a transistor.
Any ideas?
And in advance, I want to say thank you very much for any assistance you give. It's greatly appreciated!