Unknown purpose of this circuit

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

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

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 ?

KTE said:

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 ?

Click to expand...

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.??

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

Click to expand...

This reminds me of video amplifiers I used to design.

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

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.