# Electronic Design Problem (initial design).

Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
For my electronics class we were assigned a design problem given the following specifications. We had to design a amplifier that at 1kHz would have VCC of 15v, a Zi of 47k min and Zo of 4.7k max. It also needed a overall no load gain of over 1000 and the output voltage needs a capacity of at least 5v p-p. This is my design so far using Beta as 300 and Ro as 4.5k.

My questions are will it work and also what improvements can I make to help build a better circuit. This is my first design problem so any response is helpful! I attached my circuit. I will add capacitors on both 12.8K resistors but i'm not sure what value capacitors to use for them/rest of circuit.

#### MrAl

Joined Jun 17, 2014
8,357
Hi,

Real quick reply...

You have a 1Hz input there? Or is it supposed to be 1kHz?

The input capacitor may be too small for 1Hz. Did you check the approximate 3db cutoff point of the input section using that capacitor value?

Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
Hi,

Real quick reply...

You have a 1Hz input there? Or is it supposed to be 1kHz?

The input capacitor may be too small, even at 1kHz. Did you check the approximate 3db cutoff point of the input section using that capacitor value?
It supposed to be 1kHz I'm sorry. I don't know how to check db cutoff or really how to choose what capacitor value to use to be quite honest.

Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
For my electronics class we were assigned a design problem given the following specifications. We had to design a amplifier that at 1kHz would have VCC of 15v, a Zi of 47k min and Zo of 4.7k max. It also needed a overall no load gain of over 1000 and the output voltage needs a capacity of at least 5v p-p. This is my design so far using Beta as 300 and Ro as 4.5k.

My questions are will it work and also what improvements can I make to help build a better circuit. This is my first design problem so any response is helpful! I attached my circuit. I will add capacitors on both 12.8K resistors but i'm not sure what value capacitors to use for them/rest of circuit.

View attachment 94444

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#### Jony130

Joined Feb 17, 2009
5,241
Have you check the gain of your amp ? Because now the gain will be "very low".
Is this has to be a two stage amp? Or you could use more stages ??

Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
Have you check the gain of your amp ? Because now the gain will be "very low".
Is this has to be a two stage amp? Or you could use more stages ??
I can use as many stages as i want but i calculated the gain to be very high using equations i used in class, however that is with ought using the capacitors and AC values since we never learned that...

#### Jony130

Joined Feb 17, 2009
5,241
Can you show us this equations?

Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
These are my calculations.

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#### Jony130

Joined Feb 17, 2009
5,241
Aha, so you already include the capacitor in your calculation. Good for you.
As for the cap size
Ce ≈ 1/(2* pi *F* re) ≈ 0.16/(F*re)

#### panic mode

Joined Oct 10, 2011
1,882
your input signal and power source do nothing, you need to complete circuit.

Thread Starter

#### rjnachshin

Joined Nov 10, 2015
12
your input signal and power source do nothing, you need to complete circuit.
There going to be connected to ground but I'm not sure what to make my ac voltage.