Good evening, I wanted to know if you can help me identify the part of the circuit or its component, define my high frequency response, it would be the high frequency cutoff. I have already simulated their respective frequency responses, but I cannot identify which part of the circuit is what defines this high cut.
I hope you can help me. Health

 

Capacitance of D4?
Also C1, D1, D2, C2.

What is the function of Q1?

 

Capacitance of D4?
Also C1, D1, D2, C2.

What is the function of Q1?

So high frequency is defined by those capacitors?
Q1 is practically decorative.

 

C1 and C2 have no effect on the high-frequency cutoff; they affect the response time of the amplitude control mechanism.

The high-frequency response will be mainly determined by the junction capacitance of D3 and D4, acting together with R1. Since you have no idea of those diodes' capacitances, the high-frequency rolloff is indeterminate.

 

What/why Q1 B-E short?

 

In NI multisim the voltage current probe shows V/I and frequency also shows the direction of current.
You can excite any part of the circuit using different frequencies to sweep any node to see a bode plot.

I simulated a low pass this week, it is also a square to sine converter for an adjustable audio generator 10 -20 kHz range.
I developed it by sort of hit or miss trial and error. I was quite surprised to see it can produce 0.04% THD Sine.
I think quadrature along with a buffer will really further improve this by using 4 elements one for each phase.
The math is what is needed to make this really exceptional I am hopeful it is on it's way to ultra low distortion.
These guys had suggested this and it shows great improvement over what I had before. Thank you for the help

 

C1 and C2 have no effect on the high-frequency cutoff; they affect the response time of the amplitude control mechanism.

The high-frequency response will be mainly determined by the junction capacitance of D3 and D4, acting together with R1. Since you have no idea of those diodes' capacitances, the high-frequency rolloff is indeterminate.

Thank you very much, I will try to determine an approximate of it.

 

What is the output impedance of the source V1?

C1, S1, D2 and C2 will affect the frequency response.