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posted by  george smith on 11/3/2009 4:59:43 PM  |  status: Closed  |  Earned Karma: 50

Electronics Plz Help

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N/A N/A N/A N/A 11/5/2009 at 7:00:00 PM
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posted by Hemant on 11/5/2009 6:40:00 AM  |  status: Live
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Dont you think there should be β value for transistors to get atleast the gain in current
star is not the only limit

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posted by Tachyon12 on 11/5/2009 1:46:59 PM  |  status: Live
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This is a basic differential amplifier. First let us assume both the transistors are in active region( Diffential amps must always work in active region for proper functioning).

We can see that bases of both the transistors are grounded. And if we assume saturation region of operation, VBE=0.7V

So the node, where the 270kΩ and the emitter of 2 transistors meet, is at -0.7V.

Hence, the current flowing through 270kΩ = (-0.7-(-12))/270k=42μA

Since the circuit is symmetric the current must be divided equally. Hence current through 180k=21μA.

You can then find out VC by 12 - 180k x 21μ=8.22V
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