Understanding a amplifier schematics

[ku637]

Hi below is a schematics i got from a board it is for amplifiying some signal comming from the Antenna..
Can some one help me to get some insights about the two BJT configurations shown there..

Thanks for any help..

 

[chuckey]

The components on the Lh. side are to give a good input match (50 ohms?) to the input impedance of the transistor ( 2K ohms?) (C16,20,23,21,25 and the L3). C21 and C25 also isolate the DC at the base of the transistor from being shorted out. R23 and R26 provide a DC bias to the transistor Q5, so it is taken the correct current in conjunction with R28, which is decoupled to RF with C26. An amplified voltage appears at the collector of Q5 which is then given more current and appears at the emitter of Q4. The two RC circuits are meant to isolate the two outputs from each other, so if one is shorted the other still functions. As the impedance at the emitter of Q4 is very low (10 ohms?)R22 and 24 are added to bring the total impedance up to 50 ohms. The two capacitors isolate the DC at emitter of Q4 .
Frank

 

[prestonee]

The basic configuration is a 2 stage common emitter amplifier.

 

[keith1200rs]

The basic configuration is a 2 stage common emitter amplifier.

It looks more like a common emitter amplifier followed by an emitter follower (common collector) to me.

Keith

 

[prestonee]

Heh you're right, glancing can be error prone, thanks for pointing that out.