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Simple Amplifier

Chris Bargman

Mar 22, 2015
11
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Mar 22, 2015
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Hello,

I am working on building the below Amp for a school physics project however we only have very basic knowledge of resistor circuits. I have two main questions that we seem to be unable to figure out.

1) Where does the second lead on our pickup go? the diagram only shows one input
2) Where does the minus from the battery go? Again the diagram only shows the positive and I think assumes we know how this works.

upload_2015-3-21_20-36-53.png
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,878
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Jun 21, 2012
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4,878
The horizontal line at the bottom of your schematic is the circuit common or "ground" and (1) connects to the other lead of your pickup and (2) connects to the negative terminal of the battery.
 

Chris Bargman

Mar 22, 2015
11
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Mar 22, 2015
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11
If I am understanding you correct both of the missing leads should go to the common or "ground"?

I must have something else wrong then... I am still not getting anything out of my pickup.

I know I am getting power through the speaker because when I disconnect that wire I can hear the speaker make some noise...

Do you have any ideas how I can troubleshoot what else may be wrong with the circuit?
 

Laplace

Apr 4, 2010
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Apr 4, 2010
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What is the voltage on the gate of the MOSFET? Have you inadvertently reversed the direction of the zener diode? What is the source of the test signal?
 

Chris Bargman

Mar 22, 2015
11
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Mar 22, 2015
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I may have indeed had the diode backwards. I was seeing 0 volts at all 3 pins of the transistor and when i flipped it I am now seeing ~9v on all 3 pins of the transistor.

We have been a little confused about the Gate, Drain, and Source for the transistor. The way it is drawn and looking at the datasheet. It appears that I am supposed to run the left wire on the transistor to all 3 pins... as well the source and drain appear to be connected to the same thing. Is that correct?

I'm not entirely sure where the signal is coming from I have no intentional test signal it is just static from connecting and disconnecting the wire.

Thank you for the help!
 

kpatz

Feb 24, 2014
334
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Feb 24, 2014
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334
In your schematic, the MOSFET's source is on the bottom, going to ground, the drain is on top where it says 4.5V, and the gate is on the left, going to the pickup.

You'll have to look at the datasheet for the actual transistor and its package you're using to get the correct pinout. Some are arranged drain-gate-source (or source-gate-drain) and others gate-drain-source.

Here's an IRF610 datasheet: http://www.vishay.com/docs/91023/91023.pdf

It appears this transistor has the pins arranged gate-drain-source, when looking at the front of the package, pins left to right.
 
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