Unknown purpose of this circuit

[KTE]

Hello,

I am newbie in electronics and need a little help with this one. I don't have values and parameters of rezistors but i use NPN232 tranzistors with emitting area of 12 um. I am not sure about purpose of this circuit too....

Simulation would be sufficient....really appreciate the help...thanks

 

[ericgibbs]

hi and welcome.
Its a DC cascode amplifier with negative feedback and a common emitter output stage.

Where did you find the circuit diagram and what application do you have in mind.?

E

 

[KTE]

Well, I'm trying to set up the operation point, but as long as I don't know values of resistors, I am not able to...All I know the feed should be 3,3V
When running spice simulation with R1 = 35Ohms and R2 = 430....R3,and R4 are same and R5 = 100Ohms Gate>Source is not saturated enough. So I'm really struggling biasing this circuit....any ideas about the values ?

 

[ericgibbs]

Well, I'm trying to set up the operation point, but as long as I don't know values of resistors, I am not able to...All I know the feed should be 3,3V
When running spice simulation with R1 = 35Ohms and R2 = 430....R3,and R4 are same and R5 = 100Ohms Gate>Source is not saturated enough. So I'm really struggling biasing this circuit....any ideas about the values ?

hi,
Looking at the circuit , your values for R1 and R2 are far too low.
When you say 'the feed should be 3,3V', is that the supply voltage.?

I use LTSpice, if you could post your simulation with values shown, I will try to set it up in LTSpice.
E

EDIT: also what are you using as an input source.??

 

[ronsimpson]

Where did you find the circuit diagram and what application do you have in mind.?

This reminds me of video amplifiers I used to design.

 

[KTE]

Yes, the supply V1 is 3.3V and as an input ...I was trying to get DC/AC analysis and Noise with DC input 1V and AC amplitude 2V and 0 Offset. I also tried to simulate individual entities of cascode but nothing seems to work for me.

Thank you for your time, much appreciated

 

[ronsimpson]

You show a input of 1mhz. All the resistors are too high a value to work at 1mhz. You need more current flow.
I changed output pull down resistor to 1k.
Q4 pull up resistor changed, need more current.
Q2 base voltage is too low. I raised it to about 1V.
Removes Q3. Its 0.6 voltage drop does the same job as the B-E junction of Q4.
Voltage on Q1 base voltage is too low. Changed resistors to try to get the output to be at about 1/2 the supply voltage.
Now it seems to be DC stable with a output voltage of 1.7 volts.
Added a AC coupling cap to the input so I don't have to deal with DC offset.