Tuesday, April 19, 2016

Dual gate MOSFET cascode?

Another look at  the dual gate MOSFET. It could be a spin-off of a darlington pair. A darlington has two transistors on one chip. the base current of one is the emitter current of the other. Using this arrangement gives a very high gain . Input B is amplified by the first transistor producing a high input the second transistor.
What we would call a normal chain of amplifiers would be a cascade circuit. In a cascade system the collectors currents are isolated from each other and the stage are independant. You could build as many stages as you desire. With darlington circuits you must build with 'paired' transistor. Now for a look at the dual gate MOSFET.

As can be seen the chip has source 1, channel 1, drain 1 and source 2 as one element, channel 2, drain 2.
There are two transistors in series. This is called a casdode circuit. Let's take a closer look at a cascode circuit.
As can be seen here this is a common gate amp 'stacked' on a common source amp. Why would we want to build a circuit like that? I hope to answer that question next post.

No comments:

Post a Comment