Beginners Amplifier

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OmriFi Participant Join Date: Jan 2015 Posts: 1	Beginners Amplifier 01/21/2015 7:07 PM
	I've been asked to design a circuit with BJT (beta 100), and frequency response with the following terms: gain in the intermediate frequency of 39 dB, left knee frequency - 5Hz, right knee frequency - 5KHz, left slope - 20 dB/dec, and right slope - - 40dB/dec For this task I have only two DC sources of +5v and -5v.And I need the input and output resistance will be 55 ohm.No DC on the output of course and the values of the frequency response need to be with error not big as 5%. I had the frequency response as said, but not with the input and output resistance as I asked to. how can I build my circuit with smaller resistance in the input and output without affecting the the bode form? In my circuit I just connected 2 BJT's from the emitter to collector with a simple common emitter connection, but I can connect the circuit as I like.
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Anonymous Hero Guru Join Date: May 2006 Location: The 'Space Coast', USA Posts: 11119 Good Answers: 918	#2 Re: Beginners Amplifier 01/22/2015 9:20 AM
	I would isolate the filter section so that it is not dependent on loading changes at the input or output of the circuit. This is called an active filter and you can probably borrow ideas from a tone control circuit on the web. I am not that familiar with BJT (Bipolar Junction Transistors), but you might want to tap into the forums at DIYAudio as there are some very knowledgeable people there. You did not specify the input level only the amp gain. With a rail supply of ±5 VDC you have limits as to your output level. The only way around that is with a voltage doubler circuit for the power supply. Lastly, if this is a homework assignment I would encourage you to be upfront about it. You will be better served with having someone teach you about the subject than simply having someone give you the answer. I know the latter is more tempting, but understanding is the more versatile road in the end.
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