Jump to content
Electronics-Lab.com Community

Basic Transistor Circuits questions


shekhar_dandya
 Share

Recommended Posts

While designing a transistorised circuit,say a voltage divider bias,an amplifier etc,should we select the transistor first and then decide the Q-point characterstics based on its datasheet or
we establish the q-point characterstics and then select a suitable transistor?
If condition2 is correct,then what values to select for Ic for say a CE voltage amplifier?deciding that Vce = 1/3 Vcc?leaving 1/3Vcc across Rc and 1/3Vcc across Re?

Link to comment
Share on other sites

Hi

What is Q? Quiescent? Usally Q means quality in electronics, used in resonant cirquits and filters! The inverse of Q is damping. The quiescent point depends on the output demands, if you need more than 1 mA out, than a quiescent current of 1 mA is a little bit low. Also, if you need an output peak to peak voltage of 10V, than a VCC of 9V is obviously not enough.

//Staigen

Link to comment
Share on other sites

  • 3 weeks later...
  • 1 month later...

Perhaps your main concern might be noise. That will determine your choice of transistor right off the bat. Then you look at the noise characteristics of the transistor, and find out the collector current at which the transistor exhibits least noise.

What about the input impedance of the next amplifier stage? Your choice of resistors in an amplifier will be hugely influenced by this.

The source (say a microphone) will greatly influence your choice of base bias resistors. Your choice of emitter resistor will be somewhat limited by the transistor's gain, and bias current.

Perhaps you have to consider battery life. This means your design should draw as little current as possible, usually implying large resistances.

Any amplifier design is a compromise based on these kinds of considerations.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.