Current Buffer –
The ULN2001A, ULN2002A, ULN2003 and ULN2004A are high voltage, high current darlington PIN CONNECTION arrays each containing seven open collector dar- lington pairs with common emitters. Each channel rated at 500mA and can withstand peak currents of 600ma.
WHERE TO USE:
These versatile devices are useful for driving a wide range of loads including solenoids, relays DC motors, LED displays filament lamps, thermal print- heads and high power buffers in the situations when the input signal is not providing enough currents. E.g. we need to drive a relay or DC motor according to the signal given by some IC.
HOW TO USE:
Suppose we need to drive DC motor and the motor needs a specific amount of current. It’s in the range of 30-100 mA. But such high currents cannot be delivered by simple ICs or parallel port etc. Hence we need a current buffer for that. So we select Uln-2003 in this case.
The pin connection of ULN 2003 is as follow:
The ULN 2003 is an inversion buffer and hence output is taken from pin 9 and the output pin.
If we are driving motor according to the signal from some IC which is not able to provide enough current, then
- Firstly we input that signal to one of the 7 input pins of ULN 2003, say pin 1.
- Then output I taken from the Pin 9 and the corresponding output pin i.e. pin 16 as shown below:
- We also connect a high current power source of appropriate voltage between pin 9 and pin 8.