[63] Mosfet Body Diodes

Date: December 23rd, 2007 | Comments : [4] | Categories: DIY.

mosfet cross-section Mosfets are 4-terminal devices with a gate that controls the conduction of the drain to source channel. The body (or substrate) of the typical n-channel enhancement mosfet is a P-type material with the drain and source formed from N-type materials.

The oxide layer insulates the metal gate connection from the other layers. There are holes in the oxide layer left for the metallic contacts of the drain and source.

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[60] Mini-Booster: Fat and Fatter

Date: December 12th, 2007 | Comments : [16] | Categories: DIY.


Fat switch


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[59] Epiphone Valve Junior mods

Date: December 7th, 2007 | Comments : [6] | Categories: amps, tubes.

Epiphone Valve Jr. head


My new Epiphone Valve Jr. amp head

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[58] Pulldown Resistor vs. Input Impedance

Date: December 3rd, 2007 | Comments : [3] | Categories: DIY.

I sometimes get the question “Does a pulldown resistor affect input impedance?”. The short answer is “Yes”.

As we see here, the guitar pickup is modeled as a signal source in series with an output impedance (Z1).

When you add the pulldown resistor at the input of a pedal circuit, that new resistor becomes the maximum impedance (Z2) into which the pickup is looking. It can never be higher than the value of the pulldown, even if the circuit input impedance is infinite.

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