Hi everyone,
I am a mechanical engineering student and I need to develop an electric circuit. I designed the circuit with Pspice, but then I needed to implement it in Simulink. In the circuit, I have npn and pnp transistors (tip31c, tip32c) and in Simulink I cannot pick up the model of the transistor directly, but I need to specify some properties from the datasheet.
I am asked to insert:

• the forward current transfer ratio h_fe: in a datasheet 3 different values of h_fe are specified, and I do not know the difference among them
  
• Ic and Vce at which h_fe is specified: I found them in the datasheet
• output admittance h_oe: I guess it is Ic/Vce with the values of point 2
• Voltage Vbe: I found it in the datasheet
• Current Ib for voltage Vbe: in the datasheet I found Ic for Vbe, thus I divided Ic by h_fe. Is it correct?
• Reverse current transfer ratio: no idea about what it is, set to 1
• Collector and Emitor resistances: I have no idea where to find them

 

it would help if we had a schematic. what is the circuit supposed to do? do U want small-signal parameters, or DC measurements (the two are quite different)? is it possible for U to get the needed parameters from Pspice?

 

it would help if we had a schematic. what is the circuit supposed to do? do U want small-signal parameters, or DC measurements (the two are quite different)? is it possible for U to get the needed parameters from Pspice?

Hi, thank you for your answer. The circuit is shown in the attached picture. The input is a current source, sinusoidal in this case. Everytime the voltage has a minimum or a maximum, the circuit let the current flow through the inductor, so to reverse the voltage and increase the magnitude of the voltage on the load. I simulated it with PSpice and it works, but with PSpice I just chose from a catalogue the transistors I needed, I did not need to specify anything.
Honestly, I do not know the difference between DC parameter and small-signal parameters.
I tried to get those values from PSpice but honestly I did not find anything.

Lorenzo

 

i'm guessing by the name of your drawing that U are studying piezoelectrical effects; piezoelectric crystals are used in electrical circuits that need humungous inductors (with L > 1 H, etc.) so as to get a very high Q for the circuit; hence the current source as a driver, and using the inductor to convert the input current signal to a voltage. the problem U are having is that the parameters U need aren't necessarily directly available on the datasheet, if at all; instead, they need to be calculated from curves. in the real world, I would suggest measuring the values yourself, but even that isn't always practical for a student who isn't well-versed in electronics.

since U are defining a custom device in Simulink, U might want to look at the corresponding function in Pspice. in other words, check Pspice to see if there is a way to define a custom device; it almost certainly does have such a function. with any luck, it will not only let U define a custom device, it will also let U start with an already-defined device (namely, a TIP32C or TIP31C) as a base from which U can work by modifying its characteristics. it has been over 20 years now, but i once worked with a circuit simulator that had such functionality; the problem i had with it was that i was not allowed to "copy" some devices because of software licensing issues (gotta love proprietary software!). if that isn't available, U might be stuck with googling for the parameters.

 

I tried to follow your advice but the new situation is like the one in the picture:

I would like to use my transistors to have the situation described by the dashed blue line, whereas with simulink the situation I got is the one in the black-yellow picture: the circuit opens at every maximum as I wish, but at some point the voltage stops dropping and starts increasing again. I really have no clue what the problem can be.

 

Post the circuit you are simulating.

 

Post the circuit you are simulating.

This is the circuit. The simulation with PSpice work, but I am not able to get a proper result in Simulink.. I don't know whether it is because of the trainsistor or because of the diodes. Appereantly, since the voltage is reversed at every max/min the transistor work properly, but I am not sure

 

Since it's not apparent where those various waveforms in post #5 are from on the circuit it's difficult to say what the problem is.

What is the purpose of that circuit?

 

Since it's not apparent where those various waveforms in post #5 are from on the circuit it's difficult to say what the problem is.

What is the purpose of that circuit?

The purpose of the circuit is to let the current flow on the inductance every time the voltage reaches a maximum, so to create an electrical oscillator through the inductance and invert the voltage value. The original voltage is sinusoidal; once it is inverted after each max/min the transistor open again, and the voltage increases/decreases in a sinusoidal trend again.

 

That's what the circuit does.
But what's the purpose of doing that?
Why do you want that odd current flow?

 

Hi.
It seems strange to me to include the diodes D7 and D8 (direction).

 

http://alltransistors.com/transistor.php?transistor=46862

Hi, click this link to see tip32c datasheet that will help you.