Hello everyone, I have been given the assignment to design an LED driver using a BJT(or MOSFET or combination, I cannot use opamps). The circuit is supposed to act as a buffer and adhere to the following specs listed below.
1) High input impedance --> Thus the common collector.
2) High current gain
3) To be able to drive the led using the Philips RC‐5 protocol.
The LED I have been given to work with is the tshg8400 datasheet:
https://www.vishay.com/docs/81297/tshg8400.pdf.
I modeled most of the parameters of the LED needed for the AC analysis (some I left untouched). (picture below)
So far I the circuit is behaving amazingly in DC. (Without the output capacitor)
My issue begins when I try to do an AC analysis on the circuit. When the output capacitor is added, almost no current flows through the diode.
The voltage gain as expected of a buffer circuit follows the input voltage but I cannot figure out why the current gain is so low.
As for the frequency part of the protocol the values of the input and output capacitor I will change later to get the needed response.
I would love your feedback on that because I could not find a solution to this still.
I am not sure about my analysis parameters so I posted them as well just to be safe.
Thank you in advance.