This is a circuit I made recently; a differential bjt amplifier (without any signal, only DC).
So I was trying to see, what happens when I change the voltage difference between the base of Q1 and base of Q2. Q3 represents constant current source.
According to the example shown here: https://www.youtube.com/watch?v=mejPNuPAHBY , with changing the Vbe drop across Q1, the I_e1 should change inversely proportional to I_e2. As the I_e1 increases, I_e2 decreases.
Well, I tried to achieve that, but it didn't happen as said. If 5M potentiometer would be removed, the both of I_e would have a value of approx. 550uA. As I connected the potentiometer into the circuit and changed it, I_e1 was decreasing but I_e2 didn't change a bit (pictures given down below).
- Where is the glitch in this circuit, as differential pair doesn't behave as it should?