Since Q1 and Q2 are emitter followers, they do not speed up the rise/fall times of the 121 output stage. Also, they decrease (by over 10%) the max Vgs available to enhance the FET in a circuit where that parameter already is questionably low. Why are they in there?

They give a low output impedance to drive the high input capacitance of the FET.
I'm surprised you didn't know that.

 

I don't really get your answer. Do you mean if I search for an another power MOSFET, I can remove Q1 & Q2?

I'm saying that is a real possibility based on device improvements over the past few decades. Plus, if you tune the MOSFET to the specific characteristics of the load, you might be able to use a smaller device with a lower gate charge. The rule of thumb is 2:1. If the load runs on 12 V, use a 30 V FET. If the peak load current is 1 A, use a 2 A FET.

ak

 

They give a low output impedance to drive the high input capacitance of the FET.
I'm surprised you didn't know that.

I do know that. My point is that with a more optimal FET they might not be needed.

ak

 

I was looking back for a moment at my monostable multivibrator at the voltage. I don't really get why I get a voltage of 300mV... The voltage I was expecting was about 3.4V (in datasheets). Did I do something wrong?
Thanks in advance

 

I was looking back for a moment at my monostable multivibrator at the voltage. I don't really get why I get a voltage of 300mV... The voltage I was expecting was about 3.4V (in datasheets). Did I do something wrong?

You didn't account for the 10:1 reduction in the displayed voltage due to the 10:1 probe.

 

You didn't account for the 10:1 reduction in the displayed voltage due to the 10:1 probe.

wauw.. feeling stupid right now haha
thanks