# high frequency

#### SaurinM

Joined Jun 20, 2020
6
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

#### MrChips

Joined Oct 2, 2009
21,400
Capacitance of D4?
Also C1, D1, D2, C2.

What is the function of Q1?

#### SaurinM

Joined Jun 20, 2020
6
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.

#### OBW0549

Joined Mar 2, 2015
3,459
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.

#### ronsimpson

Joined Oct 7, 2019
727
What/why Q1 B-E short?

#### sparky 1

Joined Nov 3, 2018
265
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

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#### SaurinM

Joined Jun 20, 2020
6
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.

#### MrChips

Joined Oct 2, 2009
21,400
What is the output impedance of the source V1?

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