I need help with the following configuration , using LIRC for as the source signal for infrared led transmitter circuit with raspberry pi .
when putting the infrared led emitter led above the collector , I couldn't get enough range for led ( wasn't bright enough using a digital camera ) even with higher voltage and current ( 5 volt )
so I've chosen the following configuration to get current gain without voltage gain , the led was bright and got range about 6 meters and even can handle 2 IR leds in series .
my question :
1- I know the emitter follower configuration has a current gain and no voltage gain ( the IR led can handle up to 1.5 A for a short time of pulses ) , so how can i calculate current flowing from the emitter to the IR led .
2- if the emitter follower has no voltage gain , it should have voltage drop about .7 , so vout should 3.3-.7 = 2.6 volt . I have used a digital mulitmeter between the emitter and ground and shout that voltage is about .2 volt . so , is it a wrong reading ? how could the led be bright if the IR led typical forward voltage is 1.3 volt ?
how can I calculate current of Ie ?
3- how can I simulate IR pulses using ltspice (generting squrewave from independent signal source tool)
attachments : example for IR pulses http://bit.ly/1N4GHRv