could you tell me how to analyze this circuit?

Thread Starter

parksangtae

Joined May 23, 2021
5
20210608001832.png


I designed a circuit like this.

originally, i put jfet(n-cha) on Q2,Q3,Q4. however we don't have stock now. so i use transistor and i will use satuation state, cutoff state.

2n2222's collector-emitter-satuation-voltage is 0.3~1 and current gain is 100. so i must controll current. but I can't analyze this circuit.

how can i analyze this circuit??
 

ericgibbs

Joined Jan 29, 2010
12,974
I designed a circuit like this.
hi park,
As you designed the original circuit, can you explain what the circuit was supposed to do.?
How is the LM324 powered.
I see there is now a dot on the track.
E
 
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MaxHeadRoom

Joined Jul 18, 2013
23,150
Your wire termination points are not clear, not much difference between a crossing and a termination!
Also power common shown as earth GND, is this required?
 

Papabravo

Joined Feb 24, 2006
16,188
The purpose of the circuit eludes me. JFETs or BJTs, the result is still the same. It looks like the classic joke about building a Write-Only Memory circuit.
 

Irving

Joined Jan 30, 2016
1,573
Hmmm, the output stage looks remarkably similar to the TS' other post here, so I'm guessing this is some sort of motor control but the output of the LM324 couldn't drive any motor I can think of ; The LM324 is being operated as a comparator but it makes no sense to me. I have a sneaking suspicion that Q1/Q2/D1 is supposed to be some sort of temperature measuring arrangement, Q1 being a constant current into base of Q2 (maybe?).
 

MrAl

Joined Jun 17, 2014
8,262
View attachment 240618


I designed a circuit like this.

originally, i put jfet(n-cha) on Q2,Q3,Q4. however we don't have stock now. so i use transistor and i will use satuation state, cutoff state.

2n2222's collector-emitter-satuation-voltage is 0.3~1 and current gain is 100. so i must controll current. but I can't analyze this circuit.

how can i analyze this circuit??
Where is the output?
Also, what is the marking of that last resistor on the far right it is hard to read what the label says.

There are some things that dont immediately make sense such as what that capacitor C2 does. Does ti act to delay the rise of the voltage at the cathode of D2 slightly.

Is this circuit supposed to have a motor connected to the output?
 

MrAl

Joined Jun 17, 2014
8,262
For starters, Q2 does nothing useful.
That appears to be true of the whole circuit.
If this entire circuit does anything useful it would have to be something subtle, probably very subtle.
But since anyone that can design a very subtle acting circuit would certainly know enough to label the output and since some things dont make too much sense, such as where the output(s) is (are) to be taken from, i have my doubts it does anything at all :)
Oh wait i am wrong, it wastes parts.
Maybe a Rube Goldberg circuit? The entire circuit is a circuit that provides a voltage level one diode drop from Vcc. ha ha.
 
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Irving

Joined Jan 30, 2016
1,573
There are some things that don't immediately make sense such as what that capacitor C2 does. Does it act to delay the rise of the voltage at the cathode of D2 slightly.
Q3/Q4/C2/etc do have a purpose in the right context. When power is applied to that 'sub-system', Q3 is on, holding Q4 off. C2 charges through D2. When power is removed D2 blocks, C2 turns on Q4 through R5+R13. Makes no sense until you replace the output 'resistor' with a DC motor; D3 blocks reverse EMF from motor and Q4 shorts motor with R6, thus acting as a brake (though R6 really needs to be much smaller).
 

BobaMosfet

Joined Jul 1, 2009
1,780
View attachment 240618


I designed a circuit like this.

originally, i put jfet(n-cha) on Q2,Q3,Q4. however we don't have stock now. so i use transistor and i will use satuation state, cutoff state.

2n2222's collector-emitter-satuation-voltage is 0.3~1 and current gain is 100. so i must controll current. but I can't analyze this circuit.

how can i analyze this circuit??
Title: Understanding Basic Electronics, 1st Ed.
Publisher: The American Radio Relay League
ISBN: 0-87259-398-3
 
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