How Does Cascading Common Emitter Transistors Affect Signal Amplification?

AI Thread Summary
Cascading common emitter transistors can significantly amplify signals, with the first transistor converting microamperes to milliamperes at its output. The second transistor further processes this output, responding to the increased current from the first. In a typical setup, the first transistor acts as a current amplifier, while the second serves as a voltage amplifier. For example, a 10-mV input can yield a 150 mV output, demonstrating effective amplification. Understanding the roles of each transistor in the cascade is crucial for optimizing signal amplification.
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The ouput of common emitter transistor 1 is connected to input of common emitter transistor 2.
Please explain about the input and ouput signal (ac).
1.Is there any amplification after the transistor 1?
Normally the input is in uA, the output is in miliA
2.Is there any amplification after the transistor 2?
The output from transistor 1 is in miliA, how should it responsed by the transistor 2?
 
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In the thumbnail, a 2-transistor common emitter (differential) amplifier is followed by an emitter follower (Q3). The first transistor (Q1) is a common-collector (emitter follower) current amplifier, and the second transistor (Q2) is a common-base voltage amplifier. A 10-mV input signal gives a 150 mV pulse out. Is this what you mean?

Bob S
 

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