# to change a transistor amplifier circuit, to get 2v in output.

Discussion in 'Homework Help' started by Altynbek Tanbayev, Apr 9, 2016.

1. ### Altynbek Tanbayev Thread Starter New Member

Apr 9, 2016
2
0
Hello everyone! I am new in electronics and need some help. The task was to get 2v output signal from 20 mV input with help of transistors(as less- two). I've build a circuit on multisim and it gives me only 711 mv. Can anyone help me. What should i change to get necessary signal?
Also there must be 32 Ohm load.
Thank you

2. ### Altynbek Tanbayev Thread Starter New Member

Apr 9, 2016
2
0
P.S. 20 mV input signal and 2v output signal - Peak to peak

3. ### #12 Expert

Nov 30, 2010
16,671
7,314
Start by calculating the necessary gain. 2V/0.02V = 100
Then calculate the current needed to deliver to the load at peak voltage conditions.
Increase the current in both stages.
Build too much gain into the circuit then use a negative feed back configuration from collector Q3 to emitter Q1.

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4. ### Ramussons Active Member

May 3, 2013
562
92
The biasing resistors R1, R2 and R6,R7 also need to be much higher. With the present values, they will load the previous stage.

AAC Fanatic!'s is the correct approach. Gain is to be controlled by feedback.

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Nov 30, 2010
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6. ### Ramussons Active Member

May 3, 2013
562
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OOPS! Sorry #12

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7. ### #12 Expert

Nov 30, 2010
16,671
7,314
On second thought, taking the feedback point after C5 would use one less part.

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8. ### MrChips Moderator

Oct 2, 2009
12,624
3,451
For 32Ω load you have to redesign the output stage to handle such a low impedance.

First step, change R10 from 32Ω to 5kΩ only to test the simulation.
Increase R4 and adjust for overall gain of 100.
Now add an additional transistor stage in a common collector configuration. Take the output off of the emitter resistor.

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9. ### Bordodynov Active Member

May 20, 2015
670
194
Need a push-pull stage. That's about if we add one more transistor, it is possible to create a scheme without settings.
See: