Problem-1
Your input signal is 10 volts peak, or 20 volts p-p.
Your supply for the amplifier is 10 volts.
The gain is about 2.
10 volts in 20 volts out peak with only a 10 volts supply.
Change the input signal to 1 volt pk and see what happens.
1V in pk, 2V p-p in
gain=2
output = 2V pk or 4V p-p.
Problem-2
The DC model shows almost 0 volts across the transistor, C to E.
You need to change the bias point.
Cut R2 in half. (2200 approximately). You need voltage across C to E.
linear amplifier with voltage-divider bias
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17th April 2012 02:19 AM #1mockingbird
linear amplifier with voltage-divider bias
My lab homework is to use Multisim to design a linear amplifier with voltage-divider bias. We are using an example in the textbook as a template. Values for Vcc and the first four resistors were given from an example we did in the previous chapter. It looks like it should be easy, but my Vc isn't right. Here is a screenshot:
120416.jpg
If I let it run long enough, Vc actually starts to approach 0. Whatever I did wrong is beyond my current level of comprehension. Will anyone please help me troubleshoot this?
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17th April 2012 02:56 AM #2ronsimpson
0
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17th April 2012 03:43 AM #3
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19th April 2012 02:53 PM Thread Starter #4mockingbird
Thank you both for the responses. I have made (I think) the recommended alterations to my circuit, with unsuccessful results. How do I establish VCE? In my notes, I have VC=VCC-ICRC. Are you saying the transistor is operating in saturation?
120419.jpg0
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19th April 2012 03:07 PM #5
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19th April 2012 04:34 PM #6JimB
At the risk of appearing a bit harsh, I am not surprised with that schematic.
Originally Posted by mockingbird
How is any one supposed to read that!
OK, bear with me, you seem to be making mistakes which are common in beginners by having wires un-necessarly crossing all over the place, and components which do not line up, leading to dog-legs in the wires.
All this contributes to a lack of clarity and understanding.
Please look at my redraw of your simulator schematic, I hope that you find it easier to understand than your original.
JimB0Experience is directly proportional to the value of the equipment ruined.
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21st April 2012 05:09 PM #7audioguru
It would be nice if you turn off the dots on the schematic that are all over the place.
0Uncle $crooge
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22nd April 2012 05:15 AM Thread Starter #8mockingbird
Not harsh at all JimB, for my level of experience. Your redraw is easier to understand. I find it easier to draw these by hand. If I was better with drawing in Multisim, I might have caught on to what Roff was saying earlier.
I have to be at work in 7 hours and I am up way past my bedtime studying circuits...
120421.jpg
I have added yet another dot to the circuit, this one connecting the base to the voltage divider, as was kindly suggested earlier. I haven't checked the math, but the output looks like what I expected from the beginning.0
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22nd April 2012 07:25 AM #9JimB
Still a few odd unnecessary kinks in the wires, but much better and more understandable. Keep it up.
JimB0Experience is directly proportional to the value of the equipment ruined.
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22nd April 2012 09:14 AM #10Winterstone
I am afraid you forgot the dc drop Ic*Re across the emitter resistor, didn't you? Originally Posted by mockingbird
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