electronic amplifier design (2nd attempt)

Thread Starter

rjnachshin

Joined Nov 10, 2015
12
Hi for my electronics class we were asked to design a circuit that meets the following requirements.
Zi greater than 47k
Zo has a max of 4.7k
the overall no load voltage gain is over 1000
the output voltage capacity is at least a 5v p-p with no visible distortion at 5v p-p input
Vcc = 15v

I designed the following circuit but I'm still having trouble picking the values for the capacitors and If my design meets the qualifications. I'm attaching the circuit. Im using a beta of 150 and a ro of 50k. Any feed back would be very helpful!!! If you have a better idea for how to approach the problem also please let me know.

Thank You
 

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Last edited:

marcf

Joined Dec 29, 2014
256
Yes, think you meant 5mVac for the input.

In order for 4.1k (not a standard value try 4.3k) to drop 7.5v in order to put the amp into its most linear operation, you need to have 1.8mA of collector current. With a current gain of 150 you need at least 1.8ma/150 (120uA) of base current. There is no way you are going to obtain this with a 9.48Meg (not a standard value) resistor. (15v/9.48M = 1.5uA) At 1.8ma, the 330 ohm resistor would drop a little over 0.6v. The input impedance of the amp is about 50K. (150*330ohms) in parallel with 900K (not a standard value).

This is pretty close to your goal of 47k.
 

Thread Starter

rjnachshin

Joined Nov 10, 2015
12
Yes, think you meant 5mVac for the input.

In order for 4.1k (not a standard value try 4.3k) to drop 7.5v in order to put the amp into its most linear operation, you need to have 1.8mA of collector current. With a current gain of 150 you need at least 1.8ma/150 (120uA) of base current. There is no way you are going to obtain this with a 9.48Meg (not a standard value) resistor. (15v/9.48M = 1.5uA) At 1.8ma, the 330 ohm resistor would drop a little over 0.6v. The input impedance of the amp is about 50K. (150*330ohms) in parallel with 900K (not a standard value).

This is pretty close to your goal of 47k.
 

Thread Starter

rjnachshin

Joined Nov 10, 2015
12
I have made my third design and his one has met the required goals!...well i think it did from my simulation. I need to find the parts electrical values, and the secondary rating like like power rating for resistors and voltage rating for capacitors. Also i need reference designators which I'm not sure what that means also. But I'm attaching my new design and the output waveform
 

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Bernard

Joined Aug 7, 2008
5,257
It will be hard to spec. capacitor values with unknown frequency
For 100 Hz, might aim for 3 uF for input, which is odd value so best choice 4.7 uF to 5 uF. @ 25 V or better.
 

hobbyist

Joined Aug 10, 2008
887
Could you please show us the method you used to determine the values of your bias resistors.
 

JoeJester

Joined Apr 26, 2005
4,077
Output 5v peak to peak and a gain of 1000 means the input is 5V peak to peak / 1000 or 5 mV peak to peak.

Your diagram has a signal generator at 2.5 mV rms or 7.07 mV peak to peak.
 
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