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Old 24th August 2004, 10:17 AM   #1
nbcd is offline nbcd  Romania
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Default 2n3055

hy al
can anyone give me an amplifier schematic that uses 2n3055?
I prefer i would be rated 80W or heigher
thanks
Best regards!
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Old 24th August 2004, 01:24 PM   #2
paulb is offline paulb  Canada
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Here's one: http://sound.westhost.com/project12.htm

There are also lots using the 2N3055 / MJ2955 pair.
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Old 24th August 2004, 04:37 PM   #3
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I can't understand why he is using a capacitor in series with Q1:s emitter.

Why don't use a current mirror instead?
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Old 24th August 2004, 05:12 PM   #4
jaycee is offline jaycee  United Kingdom
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The AmpsLab C70 seems to fit the bill. Not quite 80W, but near as. You could probably add another pair on the outputs and raise the rail voltage to make it 80W if you really wanted.

http://www.ampslab.com/c70.htm

Getting anything higher with those transistors is a bit of a no-no unless you're prepared to parallel a load of them. Doing that would probably be more costly than just buying MJ150003/4 or MJ21193/4, unless of course you happen to already have a large stock of N3055 / MJ2955
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Old 25th August 2004, 06:58 AM   #5
djk is offline djk
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" Post #3
I can't understand why he is using a capacitor in series with Q1:s emitter.

Why don't use a current mirror instead?"

Its the feedback loop, why would I want a current mirror there?
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Old 25th August 2004, 07:10 AM   #6
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Quote:
Originally posted by Real_Macgyver
I can't understand why he is using a capacitor in series with Q1:s emitter.

The capacitor sets the dc gain to unity.
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Old 25th August 2004, 07:21 AM   #7
nbcd is offline nbcd  Romania
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thanks all for your help
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Old 25th August 2004, 03:49 PM   #8
azira is offline azira  United States
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Quote:
Originally posted by djk
" Post #3
I can't understand why he is using a capacitor in series with Q1:s emitter.

Why don't use a current mirror instead?"

Its the feedback loop, why would I want a current mirror there?

Yes, but that isn't the complete answer. How is the DC bias controlled/evaluated if there is a cap in the emitter path?
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Old 25th August 2004, 04:22 PM   #9
Eva is offline Eva  Spain
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That transistor is biased through the 10K resistor from emitter to output. The capacitor estabilishes only the AC path. The feedback signal is applied directly to the emitter while the input signal is applied to the base

It's surprising how people gets lost when they look at amplifier schematics without long tailed pairs or current sources

Actually this old-school layout has probably higher gain and higher bandwith than any LTP with current sources
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Old 26th August 2004, 06:53 AM   #10
nbcd is offline nbcd  Romania
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Can i use BU406 instead of 2n2955?
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