VERY URGENT HELP ABOUT COMMON-COLLECTOR AMPLIFIER??

hgmjr

Joined Jan 28, 2005
9,029
If you short the emitter of either transistor to ground (assuming the presence of a emitter resistor - not shown), then you will upset the delicate balance in bias points of the direct coupled stages which will most likely cause the output transistor to either turn-off and stay off or turn-on and stay on.

hgmjr
 

Thread Starter

dogar sahab

Joined Mar 15, 2008
116
and does it make any difference in amplification if I connect CAPACITOR on the collector side of last transistor of multistage!!!..??
 

hgmjr

Joined Jan 28, 2005
9,029
The addition of a capacitor in parallel with the emitter resistor (not shown) of the last transistor will cause the gain at the lower end of the frequency range to decrease.

hgmjr
 

hgmjr

Joined Jan 28, 2005
9,029
You are correct. I should have said that the mid-band gain would be increased and the low frequency response would remain unchanged.

hgmjr
 

Thread Starter

dogar sahab

Joined Mar 15, 2008
116
now its ok..
anything confusing or important u want to tell about direct coupled ampliiers!!!??
 

hgmjr

Joined Jan 28, 2005
9,029
One thing you should keep in mind is that the a direct-coupled amplifier is very device characteristic dependent. If you replace one of the transistors with another transistor, it is highly likely that the bias settings will need to be readjusted. Another thing to keep in mind is that the amplifier's output DC operating-point will be sensitive to temperature.

hgmjr
 

Thread Starter

dogar sahab

Joined Mar 15, 2008
116
And what about the effect on the output side if I connect BY-PASS CAPACITOR across emitter in both the cases????
 

Thread Starter

dogar sahab

Joined Mar 15, 2008
116
and one more thing
What would be the case when my whole Vcc(DC SUPPLY) would appear across the output???what would be the arrangement???
 

Thread Starter

dogar sahab

Joined Mar 15, 2008
116
what change I should make in the multistage amplifier if i want the whole of DC SUPPLY VOLTAGE TO APPEAR ACROSS MY OUTPUT???
 

hgmjr

Joined Jan 28, 2005
9,029
And what about the effect on the output side if I connect BY-PASS CAPACITOR across emitter in both the cases????
The effect of placing bypass capacitors in parallel with the emitter resistors (not shown) on the overall frequency response of the amplifier will depend greatly on the size of the capacitors chosen for each resistor.
 

hgmjr

Joined Jan 28, 2005
9,029
what change I should make in the multistage amplifier if i want the whole of DC SUPPLY VOLTAGE TO APPEAR ACROSS MY OUTPUT???
One thing you would need to do is eliminate the use of a resistor in the emitter of the final stage.

hgmjr
 
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