Hi,
My name is Julio and i'm new here. This is my first thread.
So i'm studying electronics engineer and i have a mark about signal amplifier.

This is the circuit that i already calculate all point voltages and currents. I also calculate resistor RC (6K8). Now assuming that bjt Beta is 400 i need to calculate the gain for signal. So vcc and vss for signal is actually ground's so i have in first floor one EC(whit RE), after a ampop(that i don't now what is the configuration) and for the end, i have a CC(common collector).If there is no erro with my calculations AV1(EC)=-14,24V/V, AV3(CC) usually is 1. Now i'm stucked with the gain of ampop... Anyone can help me? What is the contribution of the ampop in this state?

In the practice the entire gain that i obtain is (Vout/Vin) = 10V/V, i don't now for sure if is 100 percent correct... Hope for answer's. Thanks people.

 

Has this circuit been given to you as an exercise and therefore you are stuck with it? The op-amp would perform better without the transistors, can you just get rid of them and simplify everything?

 

Yes, this circuit is given to me as an exercise, and i can't modify anything. The teacher give us the circuit and first i need to calculate all
theoretical values, like voltage, currents and gains and next i need to mout him in breadboard and make a test with wave generator...

 

Gain~R5/(Re11+26mV/3.27mA)

 

The opamp is an iv converter. The collector resistor rc acts like a CCS: the opamps noninverting terminal is at a fixed potential, so is the inverting input terminal. So the current going through the collector resistor is always the same.

The current sunk by the collector changes with the input signal, that means the current being forced into the opamp feedback resistor varies with the input.

The output transistor is an emitter follower.

The analysis is simple once you know how it works.

 

Thanks a lot! Work!