What is the difference between these two designs?

[samy555]

I know that the design fig.2 safes battery more than fig1, and that have greater input impedance?
Are there differences that are more important?
Thank you
**broken link removed**
**broken link removed**

 

[alec_t]

More important in what way? Cost? Size? Stability? .......?
If the design is to be used for AC signal amplification consider how parasitic capacitance and inductance will affect its operation.

 

[audioguru]

The circuit with high value resistors must have a high impedance load that might not be available.
Your circuits have NO load.

 

[RCinFLA]

The circuits have a combination of AC and DC feedback. What do you know about transistor input impedance versus bias levels. How do you think these input impedances would effect the loading on the feedback network.

 

[ronsimpson]

The circuit with low current is slower. (less high frequency response) The capacitance of the transistor is about the same but the RCs are much slower.

 

[MrAl]

Hi,

The main difference is the input and output impedances are different for each circuit, and the quiescent power drain is less for the circuit with the higher resistor values. Of course the other replies are equally good answers too, and after all is said and done it matters most for the application which circuit would be best. For a low power battery circuit the higher resistance values would be best if we could get away with it, but for fastest speed the lower resistance circuit would be best. If it had to be both low power and fast speed then we might find some intermediate values to use.

Very good question. If we had a way to rate questions asked on this forum i would have to rate it as one of the top questions about transistor circuits.

 

[samy555]

The circuit with high value resistors must have a high impedance load that might not be available.
Your circuits have NO load.

Good point, thank you audioguru, Greetings to family.

More important in what way? Cost? Size? Stability? .......?
If the design is to be used for AC signal amplification consider how parasitic capacitance and inductance will affect its operation.

The design is intended as a simple audio preamplifier, i.e. low freq so no need to consider parasitic capacitance and inductance.

The circuits have a combination of AC and DC feedback. What do you know about transistor input impedance versus bias levels. How do you think these input impedances would effect the loading on the feedback network.

I know all that, and I hope you give me an answer,,, thanks

The circuit with low current is slower. (less high frequency response) The capacitance of the transistor is about the same but the RCs are much slower.

Good point
please i need some more explaination about that,, thank you

Hi,

The main difference is the input and output impedances are different for each circuit, and the quiescent power drain is less for the circuit with the higher resistor values. Of course the other replies are equally good answers too, and after all is said and done it matters most for the application which circuit would be best. For a low power battery circuit the higher resistance values would be best if we could get away with it, but for fastest speed the lower resistance circuit would be best. If it had to be both low power and fast speed then we might find some intermediate values to use.

Very good question. If we had a way to rate questions asked on this forum i would have to rate it as one of the top questions about transistor circuits.

Thank you very very much
You are the only person who could understand what I meant
Some people think I do not understand the basics of electronics, and became gives me some simple basic information

Thank you again

 

[MrAl]

Hello there samy,

Well you are very welcome. And i am sure the other guys had a pretty good grasp of what was going on too they just decided to comment on one aspect and keep it short.

But your question also made me think that it would be nice if there was a "best question" vote here or something like that. They could all go into an archive.