Zz.What is the theory behind Dual Gate MOSFETs and current controlled diodes?

AI Thread Summary
Dual Gate MOSFETs feature a structure that allows for enhanced control of gain and frequency response, particularly useful in applications like high-speed transimpedance amplifiers. By AC grounding the top gate, they function similarly to a cascode stage, effectively reducing Miller capacitance. Adjusting the bias on the top gate allows for gain modulation, which was initially explored in ultrasound scanner designs. Current-controlled diodes, while mentioned, lack clarity in definition and require further exploration for theoretical understanding. Additional resources for both topics were requested but not provided in the discussion.
pottan
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Hi,

I want to know more about Dual Gate MOSFETs, i.e, their structure, working, advantages etc... Googling "Dual Gate MOSFET" didn't help at all! So please suggest some sources (online) where I can find more information on them.

Also, where can I find more information on current controlled diodes (i.e, the theory)?
 
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http://www.hamanuals.com/S1/CX7/Articles/Mosfet.pdf

I used Dual Gate MESFET before for high speed trans impedance amp design before. Basically it is like a cascode stage. The advantage is if you ac grounded the top gate, it become a cascode stage and you get rid of the Miller capacitance and increase the frequency response. By changing the bias on the top gate, you can change the gain of the stage.

In the first design in the front end of the ultrasound scanner in Siemens, the first engineer use the dual gate mosfet as a variable gain amp by adjusting the bias of the gate 1. Didn't workout very well, I changed it to a differential amp front end.
 
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pottan said:
Hi,

I want to know more about Dual Gate MOSFETs, i.e, their structure, working, advantages etc... Googling "Dual Gate MOSFET" didn't help at all! So please suggest some sources (online) where I can find more information on them.

Also, where can I find more information on current controlled diodes (i.e, the theory)?

Welcome to the PF.

Since these are schoolwork questions, you are required to do the bulk of the work on them.

Also, what is a current-controlled diode? Can you provide links to where you have heard about them?
 
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