the circuit photo blur

Thread Starter

xljin2014

Joined Nov 11, 2014
96
So what is your question about the circuit?

Ron
hi ,ron

my question is about shortly after the beginning of adding vcc, how it comes one transistor go saturation, and the other one go cut-off(right word?).

here is how I think: as vcc is added,
both transistor start to open by base resistance, but the transistors, base resistances,and collectors between are not the same exactly, so the two collector voltage are not the same.

assume left transistor's(v1) collector voltage go down faster, by coupleing of the left capacitor(c1),the voltage of the base of right transistor (v2) goes low, so v2 starts to cut off. the collector voltage stars to go up. and this voltage is coupled to v1's base, which make v1 goes to saturation.

I have two questions:
1. as I analysed before, the posative feedback happened to v1, we can also analyse v2 the same way. the difference is which one is quicker. my question is: what makes transistor go saturation or cut off. the collector goes quicker is the key?and why?
2.in this circuit, is collector voltage make sense or the voltage change make sense?I think is the second,because capacitor coupleing voltage change ,not voltage.
 

k1ng 1337

Joined Sep 11, 2020
542
Try this online simulator: https://www.falstad.com/circuit/

There is an example of your circuit under the menu "Circuits" - "Transistors" - "-Multivibrators" - "Astable multivibrator".

It's a common circuit, expect to see variations though the concept is the same.
 
Last edited:

Delta Prime

Joined Nov 15, 2019
1,326
"hi, delta

i guess the osilation circuit you recommended is different with mine"

On the contrary!
The component values may be different, the 330Ω resistors and the LEDs are positioned differently. The function is identical.
If you take the time and read the entire thread as I suggested
It will answer every single one of your questions.
Although it is not as personal as I am talking to you right now .I will only be repeating what has already been stated.With that said... if you have any other questions please feel free to ask. And the schematic in the other thread wiggles. :cool:
1648449321088.png
 
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Thread Starter

xljin2014

Joined Nov 11, 2014
96
View attachment 263723
the circuit photo uploaded is blur. is it because of low resolution?where can I make resolution higher?

Mod: Adjusted the image.

View attachment 263729
how mod adjusted the image?
View attachment 263723
the circuit photo uploaded is blur. is it because of low resolution?where can I make resolution higher?

Mod: Adjusted the image.

View attachment 263729
"hi, delta

i guess the osilation circuit you recommended is different with mine"

On the contrary!
The component values may be different, the 330Ω resistors and the LEDs are positioned differently. The function is identical.
If you take the time and read the entire thread as I suggested
It will answer every single one of your questions.
Although it is not as personal as I am talking to you right now .I will only be repeating what has already been stated.With that said... if you have any other questions please feel free to ask. And the schematic in the other thread wiggles. :cool:
View attachment 263776
1648452804708.png

this is the circuit you give1648452804708.png

this is the circuit you give me , maybe wrong link.
 

AnalogKid

Joined Aug 1, 2013
10,067
Your base resistor values are way too low
No, they are not.

I increased them 10 times and reduced the capacitor values 10 times so that the timing is the same.
Now the base resistors are way too large. Assuming the Vf of the LEDs is approx 2.0 V, the ratio of collector current to base current is now 80:1. I'm not a huge fan of the 10:1 rule, but 80:1 is way too high, even for me. With the original resistor value it was 7.4:1. I suggest you increase the base resistors to 10 K and decrease the capacitors to 100 uF. The net change in frequency is 3%.


ak
 
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