# How to change amplitude for Delta functions

Discussion in 'Homework Help' started by Kaspars, Jun 9, 2011.

1. ### Kaspars Thread Starter New Member

Jun 9, 2011
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0
Hello,

I have small problem. My input signal looks like this:

I'm using this circuit:

To get signal like in this graphic (green), so it would be impulses (Delta functions) from 0V to -0,8V:

In simulations everything works fine, but in practice I have impulses from 0V to 1V. Why so? And how I can solve my problem?

Thanks a lot

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Not sure what you are trying to achieve.

The only thing I see as strange is that V5=-0.8 volt with the source polarities as shown. Should V5 not be +0.8V, or have I missed the point?

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3. ### Kaspars Thread Starter New Member

Jun 9, 2011
17
0
Yes, V5 is +0,8V, so in the V5 exit to transistor we get -0,8V becouse of polarities.

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
OK. I'm not sure how your simulator works.

When using mine, if I were to set a DC source voltage to -0.8V that effectively reverses the nominal (annotated) output polarities. In your plots I see the simulation appears to work with the output switching from 0V to -0.8V.

When you say ".. in practice ..." - presumably you have done the simulation then actually built the circuit to see if it produces the same output at Q4 collector. You state the output pulses switch from 0 to 1V. Do you actually mean of the opposite polarity [0 to +1V] to that expected [0 to -0.8V]? How did you measure this? With a CRO?

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