EMRFD Message Archive 10164

Message Date From Subject
10164 2014-07-20 15:57:25 harizyacine transistor amplifier

Hi,

Please, I am looking for simple transistor amplifier circuit conducts and amplifies only one half of the input cycle without diode, is it possible ? 

thank you

10165 2014-07-21 09:37:09 peter_dl8ov Re: transistor amplifier
Thinking about the theory a Class B amplifier would probably do this. By altering the bias the transistor will amplify a full cycle (Class A), a half cycle (Class B) or less than a half cycle (Class C). Try this for a better explanation:

https://www.youtube.com/watch?v=c6cmkm3UPUI

Peter DL8OV
10166 2014-07-21 09:37:53 Thomas Stout Re: transistor amplifier
What you are looking for is a Class B amplifier.  You will need to bias it so that it only conducts for the half-cycle that you are looking to amplify.


10167 2014-07-21 16:58:21 harizyacine Re: transistor amplifier

Hi, thank you for your reply, if you add more explication you mean class B can amplifies half signal cycle only and biasing transistor can remove side of the signal and about the signal where ever it’s size was ? 

10168 2014-07-21 19:38:16 Will Re: transistor amplifier

Yes within reason/overloading.  If the transistor is biased so it barely conducts. When signal goes one way it will completely cut off so no conduction and thus no gain. When signal goes other way it will bias transistor on to greater or less amount depending on the amplitude. That will produce gain in circuit, on just the one half of the signal.
 
That's the nub briefly.
 
Cheers
Will
ZL1TAO
 
 
 
Sent: Tuesday, July 22, 2014 at 11:58 AM
10169 2014-07-22 17:12:12 harizyacine Re: transistor amplifier

Hi,

 ok , but if we consider that signal is RF I think it’s size will be small and such amplifier (class B) will not make it pass in one direction removing side of the signal , I think I have to use another transistor circuit or other proposition of the same circuit

thanks

10170 2014-07-22 18:36:07 David Re: transistor amplifier
If the RF frequency is high enough some will leak across anyway.

What kind of frequency and voltage level is the signal? Does it extend to DC?
How linear does the output need to be?

A single transistor shunt feedback amplifier will probably do what you want if
it is biased into class B.

On 22 Jul 2014 17:12:12 -0700, you wrote:

>Hi,
> ok , but if we consider that signal is RF I think it’s size will be small and such amplifier (class B) will not make it pass in one direction removing side of the signal , I think I have to use another transistor circuit or other proposition of the same circuit
> thanks
10174 2014-07-24 17:51:36 harizyacine Re: transistor amplifier

Hi, thank you for your reply  the frequency is about 25Mhz and the voltage  of the signal …et I don’t know the exactly but please,  if you consider some values generally then I can know how  the way is and the form of the circuit , I thinking to use resistor between the collector the base for  biasing the transistor  base if that’s compatible with the circuit 

thanks