the outcome should be like this? voltage controlled oscillator

DickCappels

Joined Aug 21, 2008
7,442
Yes, that looks about right. U3 is a sawtooth generator and U1 is a comparator with hysteresis. M1 can be a small signal NPN like 2N3904 or 2N2222 if you prefer. but add a base resistor.
 

ericgibbs

Joined Jan 29, 2010
12,932
hi thor,
This is my sim result.
Can you say what is the purpose of the circuit, you are driving the Vin with a Triangle wave.
In your first post a label is called 'audio'

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ESP_ 299.png
 

Thread Starter

thorim

Joined May 19, 2021
10
hi thor,
This is my sim result.
Can you say what is the purpose of the circuit, you are driving the Vin with a Triangle wave.
In your first post a label is called 'audio'

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View attachment 239049
Purpose: To find frequency output as we increased input voltage.
The sim graph of the triangle out should be like that? is it correct?
can you check the sim of the capacitor 10n in the schematic as it should be sawtooth graph ?
 

ericgibbs

Joined Jan 29, 2010
12,932
What are they look like and what is correct. Lastly this circuit support which range of frequency?
hi,
I would like to help you, but I need some guidance from you, regarding the specification on how you want the circuit to operate and the result you want to achieve.

ie: What is the definition of correct.?

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Thread Starter

thorim

Joined May 19, 2021
10
hi,
I would like to help you, but I need some guidance from you, regarding the specification on how you want the circuit to operate and the result you want to achieve.

ie: What is the definition of correct.?

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Our project is to compare two circuit (BJT and Op amp) as which one is work the best (performance) , our understanding if the frequency is high, the circuit will have the best performance. The correct: our graph simulation should look like this cause we dont know the graph is correct or not.
 

Attachments

Thread Starter

thorim

Joined May 19, 2021
10
Yes, that looks about right. U3 is a sawtooth generator and U1 is a comparator with hysteresis. M1 can be a small signal NPN like 2N3904 or 2N2222 if you prefer. but add a base resistor.
The opamp circuit input should be Sine , Pulse or Dc input ? which one is the suitable input?
 

DickCappels

Joined Aug 21, 2008
7,442
You will get the best performance when the input is above ground, so no real sinewaves unless offset by DC. A DC voltage gives the prettiest output. I have used this as the voltage controlled oscillator in a phase-locked loop and it responded well and locked up nicely.

All of the waveforms you mentioned will do something but the question is: For what purpose would you use this circuit?
 

ericgibbs

Joined Jan 29, 2010
12,932
hi thor,
Your question has already been answered, is there a further point you need to cover.??

If yes, please explain. but the question is: For what purpose would you use this circuit?
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ericgibbs

Joined Jan 29, 2010
12,932
hi thor,
You cannot compare the BJT Astable oscillator with OPA Triang/Square generator.

Its like comparing an apple and orange and asking which is the 'best'.;)

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