Amplifier problem that no one understand

Thread Starter

keeth

Joined Feb 17, 2018
6
Hello!
I found this place on google and thought this forum might be able to help me understand my homework.
We are 4 students who are studying abroad at San Diego State University and we need help to understand a simple
problem in our homework. Aparently language is a barrier for us after all, hehe.

The problem sound like this:

2.1 An amplifier with 40 dB of small-signal, open-circuit voltage gain, an input resistance of 1 MΩ, and an output resistance of 10 Ω, drives a load of 100 Ω.
(a) What voltage and power gains (expressed in dB) would you expect with the load connected?
(b) If the amplifier has a peak output-current limitation of 100 mA, what is the rms value of the largest sine-wave input for which an undistorted output is possible?
(c) What is the corresponding output power available?

There are no drawings or anything included in the paper what so ever.
We've are really confused as to what resistor is where. Is the input resistance the internal resistance? is there any feedback loop?

We really appriciate your help!
 

HW-nut

Joined May 12, 2016
94
I won’t answer the question directly but I can provide a few hints.

The load in combination with the output resistance forms a voltage divider which will reduce both the voltage and power output according.

For the gain calculations, you simply need to fill in the blanks on the log voltage/ power gain equations.
 

Thread Starter

keeth

Joined Feb 17, 2018
6
The load in combination with the output resistance forms a voltage divider which will reduce both the voltage and power output according.
Ok so there is a feedback involved afterall? Because that is the only way i can get this to make sence.
Or is R output the internal resistance of the amplifier?
 

crutschow

Joined Mar 14, 2008
23,521
No feedback.
The input resistance is looking at the amp input.
The output resistance is looking into the amp output (internal resistance in series with an ideal zero impedance amp).
 

Thread Starter

keeth

Joined Feb 17, 2018
6
No feedback.
The input resistance is looking at the amp input.
The output resistance is looking into the amp output (internal resistance in series with an ideal zero impedance amp).
Ok i see. I think we got it now :)
Thank you for your help!
 

Papabravo

Joined Feb 24, 2006
12,514
Would it be impertinent of me to point out that an amplifier described in words is an insoluble problem. A schematic diagram is the language of electronics. No schematic equals no useful help or communication unless both side happen to be communicating in some non-obvious way. Telepathy and crystal balls come to mind.
 

Thread Starter

keeth

Joined Feb 17, 2018
6
Would it be impertinent of me to point out that an amplifier described in words is an insoluble problem. A schematic diagram is the language of electronics. No schematic equals no useful help or communication unless both side happen to be communicating in some non-obvious way. Telepathy and crystal balls come to mind.
omg you express our feelings perfectly! Thank you! \o/
 
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