Hello,
i am a electronics student and i need to built an light emittor where a array of LEDs have to flick with a certain frequency and have a "constant" current of max200mA, to drive the leds im using an opamp and a transistor as a current regulator, and to provide the square signal im using a 555 circuit as shown in figure below.
http://postimg.org/image/p8c9qfdkx/full/
In Pspice simulator everything works as expected, however, i ve tried this circuit in pratic and the 555 oscilator works good but the signal that is in the '-' input of the opamp is not even a square wave similar to the one that entered the '+' input of the opamp, which causes the leds to emitt light but not with the square wave expected. The opamp used is an LM741.
Any idea why this is not working?
i am a electronics student and i need to built an light emittor where a array of LEDs have to flick with a certain frequency and have a "constant" current of max200mA, to drive the leds im using an opamp and a transistor as a current regulator, and to provide the square signal im using a 555 circuit as shown in figure below.
http://postimg.org/image/p8c9qfdkx/full/
In Pspice simulator everything works as expected, however, i ve tried this circuit in pratic and the 555 oscilator works good but the signal that is in the '-' input of the opamp is not even a square wave similar to the one that entered the '+' input of the opamp, which causes the leds to emitt light but not with the square wave expected. The opamp used is an LM741.
Any idea why this is not working?