Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Hybrid Pi

Status
Not open for further replies.

Micheal

New Member
Hi All,

Please help to find an expression for Beta cutoff frequency f(beta), which is simply a high frequency current-gain cutoff point of the transistor with collector and emitter terminals shorted as shown in the circuit attached.

Thanks..
Micheal
 

Attachments

  • untitled..JPG
    untitled..JPG
    10.3 KB · Views: 279
Hi Electrician,

Yup. The question exactly like this, this is the right model. Please help.

Thanks
Micheal
 
Have you tried to write the expression for the voltage appearing at the B' node with respect to an applied signal at B? It's just a simple voltage divider. Since the output is shorted, there is no further frequency dependence past B'.
 
Hi Electrician,

What should I do once I get the voltage at B' ?

Hi indulis,

What do you mean on that? What should I looking for at first? current , voltage or ...... ?

Thanks

Micheal
 
You see the dependent current source, labeled gm*Vb'e; that provides the output current, which feeds into a short.

The transconductance, gm, is not frequency dependent, so the rolloff with frequency only occurs due to the shunting effect of the two capacitors.

Calculate the voltage at B' as a function of frequency, and you've got the cutoff frequency.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top