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  #1  
Old 09-18-2010, 04:21 AM
JeromeDarshana JeromeDarshana is offline
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Red face Cascade Amplifier

hi i need to make an amplifier which has

gain of 15

output impedence of 30 Ohm

input Impedence of 30 kOhm

this must be a cascade amplifier.

can some one explain how to do the calculations ??

i need all the formulas and the was how they determine
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  #2  
Old 09-18-2010, 04:44 AM
Ghar Ghar is offline
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Don't make duplicate threads.

Formulas go with schematics, you have no schematics.
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Old 09-18-2010, 05:07 AM
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retched retched is offline
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Here is the section of our ebook that pertains to cascode amps:

http://www.allaboutcircuits.com/vol_3/chpt_4/8.html

Read. Read. Read.

The book starts here:

http://www.allaboutcircuits.com/vol_1/index.html
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Old 09-18-2010, 02:36 PM
Audioguru Audioguru is offline
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He doesn't want a cascode amplifier. He wants to cascade amplifiers or he doesn't know how so spell correctly.
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Old 09-18-2010, 02:38 PM
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Jeez a wheez.

Please forgive me. I read it incorrectly. (Or hopefully im psychic and he spelled it wrong )
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Old 09-18-2010, 04:16 PM
JeromeDarshana JeromeDarshana is offline
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i need cascade amplifier not cascode :P
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Old 09-18-2010, 04:45 PM
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Did you look at the cascade amplifiers in Google?
They are simply one amplifier that is amplified by another amplifier.

The gain is only 15 so it should be easy. The first stage can be a common-emitter transistor.
The output impedance is very low so it should have an emitter-follower or a pair of complementary (NPN and PNP) emitter-followers as the second stage.
The input impedance is fairly high at 30k so the first transistor should have a fairly low current and an emitter resistor to increase the input impedance and reduce the gain.
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